Answer:
x = 28
Step-by-step explanation:
The ratio between the sides of the big triangle (APR) and the small triangle (CDR) should be the same. So side PR divided by side AR should be equal to side DR divided by side CR. So your equation should be set up like this.
(15 + 42)/(10 + x) = 42/x
Then you solve using algebra
57x = 42(10 + x) Cross multiply
57x = 420 + 42x Use the distributive property
15x = 420 Subtract, combine like terms
x = 28 Divide, solve for x
