7x + 45 = 67
7x = 67 - 45
7x = 22
x = 22 : 7
x = 3 (остаток 1) или x = $$ 3 frac{1}{7} $$

80 : y + 77 = 87
80 : y = 87 - 77
80 : y = 10
y = 80 : 10
y = 8

25 + y = 78 - 31
y = 47 - 25
y = 22