Answer:
x = -1
Step-by-step explanation:
Given: 
Solve for x, When: 
Step by step:
1.37x + 1.08y = 16.36
x + y = 13
x = 13 - y
1.37* (13-y) + 1.08y = 16.36
17.81 - 1.37y + 1.08y = 16.36
1.08y - 1.37y = 16.36 - 17.81
-0.29y = -1.45
y = 5
x + 5 = 13
x = 13-5
x = 8
He bought 8 notebooks and 5 book covers
Answer:
475 mph
Step-by-step explanation:
Distance = rate × time
time = distance / rate
If x is the speed of the plane in still air:
2100 / (x + 25) = 1890 / (x − 25)
Cross multiply:
2100 (x − 25) = 1890 (x + 25)
Distribute and solve:
2100x − 52500 = 1890x + 47250
210x = 99750
x = 475
Answer:
1. distance = sqrt( (7-7)^2+(2- -8)^2) = 10
2. check out desk (0,0 ) => distance = sqrt( (0- -9)^2+(0-0)^2) = 9
3. last corner ( -3, 4)
4. area = sqrt( (-10- -10)^2+(10-4)^2) x sqrt( (-3- -10)^2+(10-10)^2) = 6x7 =42
5. check desk (0,0), south direction = negative y axis => P_beginning (0,-20), P_end (0,-(20+25)) = (0,-45)
6. A(-2,-1) and B(4,-1) lie in y =-1. AB = sqrt( (-2- 4)^2+(-1- -1)^2) =6
=> area = 3.6x6 =21.6
=> peri = 2x(3.6+6) = 19.2
7. A(-5,4) and B(2,4), AB = sqrt( (-5- 2)^2+(4- -4)^2) = 7 => AB is base
=> p = peri = 7+ 8.3x2 = 23.6
=> area = sqrt[px(p-7)x(p-8.3)x(p-8.3)]
=sqrt[23.6x(23.6-7)x(23.6-8.3)x(23.6-8.3)] = 302.8
Break the expression into group:
factor out x from 4x² - 5x : x (4x-5)
factor out 3 from 12x-15 : 3 (4x-5)
factor out common term (4x-5) :
hope this helps!
