(a-2)(a+3)-(a+1)(a-6) при а=5 целых 2 третих.

(5 2/3 - 2)(5 2/3 + 3) - ( 5 2/3 + 2)(5 2/3 - 6) = (5 • 2/3 -2) • (5 • 2/3 + 3) - (5 • 2/3 + 2) • (5 • 2/3 - 6) = (10/3 - 2) • (10/3 + 3) - (10/3 + 1) • (10/3 - 6) = 4/3 • 19/3 - 13/3 • (- 8/3) = 76/9 + 104/9 = 20

Ответ: 20