B) (7√45-6√20)⋅√5.

в) Найдем значение выражения (7√45-6√20)⋅√5.

Разложим числа 45 и 20 на множители, чтобы выделить полные квадраты:

$$45 = 9 ⋅ 5 = 3^2 ⋅ 5$$

$$20 = 4 ⋅ 5 = 2^2 ⋅ 5$$

Тогда:

$$(7√45 - 6√20)⋅√5 = (7√(3^2 ⋅ 5) - 6√(2^2 ⋅ 5)) ⋅ √5 = (7 ⋅ 3√5 - 6 ⋅ 2√5) ⋅ √5 = (21√5 - 12√5) ⋅ √5 = 9√5 ⋅ √5 = 9 ⋅ 5 = 45$$

Ответ: 45