знаки больше или меньше или равно
1 (76+53)х9...76x9+53x15
2 7x4+3x4...(7+3)x4
3 17x5+17x2...(9+8)x6
4 8x9-8x3...8x(9-3)
5 6x5-4x5...6x(5-3)
6 12x7+12x2...(7+2)x12

У вас неправильно 4) 48=48

1.(76+53)x9 < 76x9+53x152.7x4+3x4 = (7+3)x43.17x5+17x2 > (9+8)x64.8x9-8x3 = 8x(9-3)5.6x5-4x5 < 6x(5-3)6.12x7+12x2 = (7+2)x12