Because the problem tells you that the two triangles are similar, the value of a/b would be equivalent for both triangles. The fact that they are right triangles also indicates which sides are which in case the image was not drawn to scale. A is proportional to 2.1 and b is proportional to 1.4. So a/b= 2.1/1.4. This can reduce itself to 3/2 because both are divisible by .7
