We can find the value of x through a proportion. Since these two triangles are similar, their sides are in proportion.
4 is to 12 as 5 is to x
Remember to say 12, not 8! 8 is only part of the whole side. We can also simplify 4 is to 12 to 1 is to 3.
1/3 = 5/x
Cross multiply
x = 15
Hope this helps!
