5353 minutes = 89.22 hours
Maybe the figures should be 53 and 20??
Let's let Billy = A
The formula to use for work problems is
Time = (A*B) / (A+B)
53 = ( (A +20)* A) / (A +20 + A) )
53 = ( A^2 + 20A ) / (2A + 20)
A^2 + 20A -106A -1060
A^2 -86A -1060
A = 96.935
Bobby Mows in 116.935 minutes
I think the answer should be 4.7 but rounded up would be 5
X^2+ox-36=(x-6)(x+6)
x^2+0x-36=0