Решить уравнение 9/19 * B - 4/15 =11/15
9/19 * b - 4/15 = 11/15
9/19 * b = 11/15 + 4/15
9/19 * b = 15/15
9/19 * b = 1
b = 1 : 9/19
b = 19/9
b = 2 1/9