Answer:
x = 11
Explanation:
Since we are given triangle PQR is similar to triangle PTU, we can write a proportion to connect the side lengths:
PQ / PT = QR / TU = PR / PU
We don't really care about QR and TU because the are irrelevant to the problem, so we can remove them:
PQ / PT = PR / PU
Now, we can substitute the values given by the diagram:
70 / 30 = 49 / (x + 10)
We can cross multiply,
70(x + 10) = 30 * 49
And divide by 70 on both sides(too lazy to multiply :P)
x + 10 = 3 * 7
x + 10 = 21
x = 11