Answer:
Explanation:
The two triangles are similar and therefore we can set up a proportion
9/(9 + 72) = (3x - 20)/(3x - 20 + 56) Combine like terms on the right
9/(81) = (3x - 20)/(3x + 36) Cross multiply
9(3x + 36) = 81 (3x - 20) Remove the brackets.
27x + 324 +1620 = 243x Add 1620 to both sides
27x + 324 + 1620 = 243x Subtract 27x from both
1944 = 216x divide both sides by 216
x = 9
If you feel comfortable canceling the size of the numbers can be reduced.
9/81 = 1/9
1/9 = (3x - 20)/(3x + 36)
3x + 36 = 9(3x - 20)
3x + 36 = 27x - 180
36 + 180 = 24x
216 = 24x
216/24 = x
x = 9
There is another cancelation possible, but this is simple enough.