а) 4√6 + √24 - √54
4√6 = 4 √6 = 4 2.45 = 9.8
√24 = 4.90
√54 = 7.35

4√6 + √24 - √54 = 9.8 + 4.90 - 7.35 = 7.35

б) √9m - 6√m + 2√25m
√9m = 3 √m
√25m = 5 √m

√9m - 6√m + 2√25m = 3√m - 6√m + 10√m = 7√m

в) (√a + √b)^2 - a - b
(√a + √b)^2 = a + 2√ab + b

(a + 2√ab + b) - a - b = 2√ab

2/3√7 = 2/(3√7) = 2/(3 * 2.65) = 2/7.95 ≈ 0.25

а) h - 4/√h - 2
This expression seems to be incomplete or unclear. Please provide additional information.

б) x - 3√x / 2√x - 6
(x - 3√x) / (2√x - 6)
= x - 3√x / 2(√x - 3)
= x - 3√x / 2√(x - 3)

Please double-check the expression for any missing parentheses or information for clarification.