1) 920 : a = 4
a=920:46
a=20
2)2100:b=35
b=2100:35
b=60
1) 7^(x +1) ( 7 + 4) = 539
7^(x +1) * 11 = 539
7^(x +1) = 49
x +1 = 2
x = 1
2) 3^(x -2)(3² -1) > 72
3^(x -2) *8 > 72
3^(x -2) > 9
x - 2 > 2
x > 4
................................................