Solve 3x-y=-12
x+y=18

(1.5, 16.5 )

Step-by-step explanation:

Given the 2 equations

3x - y = - 12 → (1)

x + y = 18 → (2)

Adding the 2 equations term by term will eliminate the y- term

4x + 0 = 6

4x = 6 ( divide both sides by 4 )

x = 1.5

Substitute x = 1.5 into (2) and evaluate for y

1.5 + y = 18 ( subtract 1.5 from both sides )

y = 16.5

solution is (1.5, 16.5 )

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

10

step-by-step explanation: