Answer: they sold 31 soccer balls and 28 footballs.
Explanation:
Let x represent the number of soccer balls that were sold.
Let y represent the number of football that were sold.
sports store sold a total of 59 footballs and soccer balls last weekend. This means that
x + y = 59
Soccer balls cost $12 and footballs costs $18. If total sales were $876, it means that
12x + 18y = 876 - - - - - - - - -- - -1
Substituting x = 59 - y into equation 1, it becomes
12(59 - y) + 18y = 876
708 - 12y + 18y = 876
- 12y + 18y = 876 - 708
6y = 168
y = 168/6
y = 28
x = 59 - y = 59 - 28
x = 31