Hello from MrBillDoesMath!
Answer:
x = 27
Discussion:
Triangle DQC and DBR are similar by AAA so corresponding parts have the same ratio.
x /(x+18) = 39 /(39 + 26) =>
x/(x+18) = 39/65 => as 39 = 13*3 and 65 = 13 * 5
x/(x+18) = 3/5 => cross multiply both sides by x+18
x = (3/5)*(x+18) => multiply both sides by 5
5x = 3(x+18) =>
5x = 3x + 54 => subtract 3x from both sides
2x = 54 =>
x = 27
Thank you,
MrB
