Two diagonals divide a square into 4 congruent triangles. The base of each triangle is 8 inches and the height is 5 inches. What is the area of the square?

80

Step-by-step explanation:

1. Find an area of 1 triangle:

5x8x1/2=20

2. Multiple by 4

20x4=80

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18