Question 257654
Start by assigning variables to the unknown quantities:
B = weght of baseball.
S = weight of soccer ball.
F = weight of football.
From the problem description:
1) B+F = 1.25 lbs.
2) B+S = 1.35 lbs.
3) F+S = 1.6 lbs.
Now you have a system of three equations with three unknowns and this is solvable.
Rewrite equation 1) as (B = 1.25-F) and substitute into equation 2) to get:
2a) (1.25-F)+S = 1.35
Now rewrite equation 3) as (S = 1.6-F) and substitute into equation 2a) to get:
2b) (1.25-F)+(1.6-F) = 1.35 Simplify and solve for F.
2c) 2.85-2F = 1.35 Add 2F to both sides.
2d) 2.85 = 1.35+2F Now subtract 1.35 from both sides.
2e) 1.5 = 2F Finally, divide both sides by 2.
{{{highlight(0.75 = F)}}} The football weighs 0.75 lbs.
Now that you know the weight of the football (F = 0.75) you can substitute this into equations 1) and 3) to solve for B and S respectively.
I'll leave this for you to finish up.
Good luck!