Here is the are of the shaded region
shaded = rectangle - parallelogram
245 = 20(3a-10) - 5(2a-9)
Keep in mind that:
- area of a rectangle = length * width
- area of a parallelogram = one side length * consecutive side's length
So, we have:
245 = 60a - 200 - 10a + 45
solve for a now:::
245 = 50a - 155
50a = 245+155 = 400
a=400/50 = 8
a=8I hope you got the idea