He used 53 pounds. I got this by using two equations. a+b=117 and 5.8a+4.1b= 569.8
I took the first equation and subtracted 'b' so the equation looked like a=117-b. I then plugged in 117-b into the second equation, so it ended up looking like this: 5.8 (117-b)=569.8 5.8 times 117 is 678.6. And 5.8 times negative b is negative 5.8b. The equation now looks like this: 678.6-5.8b+4.1b=569.8 Add like terms 678.6-1.7b=569.8 Then subtract 678.6 from both sides -1.7b= -108.8 divide each side by -1.7 you get b= 64. But because you are looking for how many pounds for a, subtract 64 from 117. You get 53. 53 is the answer.
