Ok so you can see 2 triangles that i highlighted, flip it so it is the same direction as you can see from the drawing
using the similar triangle equation
you get
136/64 = x/136
cross multiply and get
64x=18496
x=289
hope it help
using the similar triangle equation
you get
136/64 = x/136
cross multiply and get
64x=18496
x=289
hope it help