1) 450/у = 9*10
450/y = 90
y = 450/90 = 5
2) 56/(14 - n) = 7
14 - n = 56/7 = 8
n = 14 - 8 = 6
3) (48/x) + 15 = 23
48/x = 23 - 15 = 8
x = 48/8 = 6
4) (1200/a) - 29 = 31
1200/a = 31 + 29 = 60
a = 1200/60 = 20
5) (45/a) + 6 = 11
45/a = 11 - 6 = 5
a = 45/5 = 9
6) (30 - a)/3 = 6
30 - a = 3*6 = 18
a = 30 - 18 = 12
7) a*a + 36 = 72
a² = 72 - 36 = 36
a = √36
a = 6; a = -6