I need help I don't know where to start or what to do I need guidance.

Question

Triangle A,B, and C have the ratio of the sides of triangle A to triangle B is the same as ratio of the sides of triangle B to triangle C.
Triangle A has a base of 5 , Triangle B shows no base # , Triangle C has 45 as base.

Answer 1

A/B=B/C
Multipy both sides by BC
A*C=B*B
A*C=B^2 take the square root of each side
B=sqrt(A*C)=sqrt(5*45)=sqrt(5*5*9)
B= 5*3=15