As the exercise says, the triangles are similar. So, we can set up proportions between correspondent sides.
In order to solve for x we can set up the proportion between the horizontal and vertical sides:

Solving this proportion for x implies 
Now you can solve for m and p using the pythagorean theorem, because both triangles are right:

Then, we know that the hypothenuse of the big triangle is m+p, so we have

which implies

First we find the common difference...to do this we subtract the first term from the second term. -7 - (-1) = -7 + 1 = -6
now we are going to find the 10th term
an = a1 + (n-1)*d <== formula for finding any term in arithmetic series
a1 = 1st term, d = common difference, n = term we want to find
now we sub
a10 = -1 + (10 -1) * -6
a10 = -1 + (9 * -6)
a10 = -1 - 54
a10 = - 55
now we will find the sum
Sn = (n (a1+ an)) / 2 <== formula for finding the sum
S10 = (10(-1 - 55))/2
S10 = (10(-56) / 2
S10 = -560/2
S10 = - 280
so the sum of the first 10 numbers is -280
Answer: x = 780
Step-by-step explanation: Well <u><em>percent</em></u> means <em>over 100</em> so we can set up an equation for this problem by reading it from left to right.
So we know that <u><em>10%</em></u> means <em>10/100</em>, <u><em>of</em></u> means times, <em><u>what</u></em> <em><u>number</u></em> means <em>x</em>, <u><em>is</em></u> means <em>equals</em>, and <em><u>12</u></em> means 12.
Notice that <em>10/100</em> can be reduced to 1/10.
So rewriting our problem we have <em>X/10 = 78</em>.
To get rid of the fraction, we multiply both sides of the equation by 10 and we have <em>x = 780</em>. So, 10% of 780 is 78.
Now let's check our answer back in the original problem to see if it makes sense.
We have <em>10% of 780 is 78</em>. Well we know that 100% of of 780 would be 780 so 10% of 780 should be alot less than 780 so 78 seems to make sense.
Image provided showing my work.
Answer: 9 L
Step-by-step explanation:
Given
The dimension of the rectangular container is 
It is filled with
of the height
Water present in the container

Also, 

Now, half of the water is poured out
So, half is left

Thus, 9 L of water is left in the container
Answer:
y = -1/2x +1/2
Step-by-step explanation:
Point B is 4 up and 2 over from point A. So, the midpoint will be 4/2 = 2 up and 2/2 = 1 over, at (1, 0).
The ratio of rise to run between A and B is ...
m = rise/run = 4/2 = 2
The perpendicular line will have a slope that is the opposite reciprocal of this, -1/2.
Then the point-slope equation for the perpendicular bisector is ...
y -k = m(x -h) . . . . . line with slope m through point (h, k)
y -0 = -1/2(x -1) . . . .line with slope -1/2 through point (1, 0)
y = -1/2x +1/2 . . . . simplified to slope-intercept form