This is because all the angles in a triangle are supplementary which means they add up to 180 degrees. This means that you subtract 180 from the other two angles
A is right because you would use y as miles and x as time multiplied by 40 the constant and then plus 18 for the previous miles. C is right because 18 is the initial value with 18 being added
This is an algebraic equation. First we have a square the width is X The length is L=3X-2. P (perimeter is 44) Therefore P = 2L+2X = 2(3x-2) + 2x = 6x - 4 + 2x = 8x - 4 44+4=8x x=48/8 x=6