Hey there! :D
The biggest thing to remember here is the similar triangles and their side lengths.
Okay, so we can separate these triangles into 3 similar triangles. Which, we only need to do that to two for a proportion, but if you were to have more variables, you could separate the triangles even more if you needed to.
We want to find two triangles that have "x" has a value of their side, so we can solve a proportion.
The bigger triangle, (the whole two triangles combine) and the smaller triangle on the left can be used to make a proportion.
On the smaller triangle:
We have 9 cm on the shorter side and x as the hypotenuse.
On the larger triangle:
We have x as the shorter side, and then 25 as the hypotenuse. (9+16)
Note: You have to flip the larger triangle upside down to make it a similar structure to the other two triangles. It is similar, you just have to flip it.
So, now we can make a proportion.

Now, cross multiply.
9*25= 225
x*x=

So, find the square root.
√225= 15
x= 15. I hope this helps!
~kaikers
Answer:

Step-by-step explanation:
The formula for area of a rectange is lw, where l is length and w is width. Since x-4 and 5x+2 are the sides, we can multiply them together to give us the area. We do (x-4)(5x+2). We use the FOIL method (First Outside Inside Last) and get 5x^2-18x-8.
The answer for this problem is 125
Step-by-step explanation: Using the equation, y = mx + b, the slope-intercept form, plug in the values you have and solve for b. (m is the slope.) You have y = -8 and x = 4 and m = 1/2.