Question

This is hard can I get help

Answer 1

Same as the last one you asked. 

AB + BC = AC. Just think of it like Part + Part = Whole Thing

(2x + 6) + (6x + 5) = 51

Combine like terms:
8x + 11 = 51

Subtract 11 from both sides to get the variable and its coefficient on its own:
8x = 51 - 11
8x = 40

Divide both sides by 8 to isolate the variable:
x = 5

It's asking for us to find BC so now we plug in x = 5 to the equation it gave for BC. 

6x + 5
6(5) + 5
30 + 5
35

BC is 35 units long.