What you need to do is do the formula of Area=1/2×Height (Base B +Base A) Base B is bottom Base A is the top then you divide by 2 In this case 1/2 ×8/1 ×(12+15)=108
1: Solve for either x or y in one of the equations. So x + y = -1 is y = -x -1
2: substitute the new equation in the opposite equation. So x - (-x - 1) = 7
3: distribute the negative. X + x + 1 = 7
4: combine like terms. 2x + 1 = 7
5: solve for x. Subtract 1 on both sides. 2x = 6
6: divide by 2 to get x by itself. X = 3
7: plug the new value of x into one of the ORIGINAL equations. 3 + y = -1
8: solve for y. Subtract 3 on both sides.
Y = -4
9: the solution is written as (x,y) so the solution would be (3, -4)
4(a-2)=3(a+4)
4a-8=3a+12
a=20