X = 7
8(7) = 5(7) + 21
56 = 35 + 21
56 = 56
Answer:

Step-by-step explanation:
If two corresponding sides of two similar triangles are 3cm and 5cm, then the scale factor is

Two similar triangles have their area proportional with the scale factor of 
Hence,

Answer:
Step-by-step explanation: