Answer:
25 t-shirts and 35 hats were sold
Explanation:
Here, we want to calculate the number of hats and the number of t-shirts sold.
Let the number of hats be h and the number of t-shirts be t
The sum of both is 60;
Mathematically;
h + t = 60 •••••••••••(i)
The total revenue from selling h hats at $12 per one is 12 * h = $12h
The total revenue from selling t t-shirts at $18 per one is 18 * t = $18t
So the addition of this gives the total;
12h + 18t = 870 ••••••••(ii)
From i, h = 60-t; substitute this into ii
12(60-t) + 18t = 870
720 -12t + 18t = 870
720 + 6t = 870
6t = 870 -720
6t = 150
t = 150/6
t = 25
From the substitution;
h = 60-t
h = 60-25
h = 35