The missing side is 7 in
Explanation:
The information we have to know in order to solve this is that the formula of area of trapezoid is
a = 1/2h (b1 + b2)
We can fill in the information we know from the picture into the equation
15 = 1/2(3.4) (1.8 + b2)
The dimension we are solving for is b2, or base 2. To make it easier, let's replace b2 with n. Now we can solve this equation
1) Multiply 1/2 by 3.4, which is 1.7
15 = 1.7 (1.8 + n)
2) Distribute by doing 1.7 x 1.8 + 1.7 x n
15 = 17n + 3.06
3) Subtract 3.06 from both sides of the equation
15 - 3.06 = 17n + 3.06 - 3.06
11.94 = 17n
4) To isolate n, since we want one n instead of 17, we divide both sides by 17
11.94/17 = 17n/17
7 = n
