Total money earned: 1400 - 50 = 1350$
Sweatshirts sold: x
T-shirts sold: 4x + 5
Earned by sweatshirts sold: 25x
Earned by T-shirts sold: 10(4x + 5)
Equation:
25x + 10(4x + 5) = 1350
25x + 40x + 50 = 1350
65x = 1350 - 50
65x = 1300
x = 20
T-shirts sold: 4 * 20 + 5 = 80 + 5 = 85
You sold 85 T-shirts and 20 sweatshirts