Make a proportion of corresponding sides
Side AU corresponds to Side AB
Side UV corresponds to Side BC
Find AB by adding AU and UB
AU = 20x + 108
UB = 273
AB = 20x + 381
Make proportion
AU/AB = UV/BC
20x + 108/ 20x + 381 = 444/ 703
Cross Multiply
(20x + 108)(703) = (20x + 381)(444)
14,060x + 75,924 = 8,880x + 169,164
Solve for x
14,060x + 75,924 = 8,880x + 169,164
I'm sure you can figure this out
