Let the length of the diameter be d and radius be r, thus to solve for d we proceed as follows:
r²+31²=(r+15)²
solving for d we solve for r
r²+961=r²+30r+225
putting like terms together we obtain:
r²-r²+961-225=30r
736=30r
solving for r
r=24.53
thus
d=24.5333×2
d=49.067~49.1
Answer is D. 49.1
27 times..... Let me know if you want help knowing what I did. :)
Ricky works almost 7 hours if your rounding.
First of all, expand the left hand side:

Sum like terms:

Add 3 to both sides:

Subtract 3x from both sides:

So this is the solution. Every number smaller than 8 (excluded) is part of the solution of this inequality.