с примером
1,5(х+2/3)-3х-1,8
при х=1/4

Пошаговое объяснение:

1,5(1/4 + 2/3) - (3*1/4) - 1,8 =

1) 1,5 * (1/4 + 2/3) = 1 5/10 * (3/12 + 8/12) = 1 1/2 * 11/12 = 3/2 * 11/12 = 33/24 = 11/8 = 1 3/8

2) 3 * 1/4 = 3/4

3) 1 3/8 - 3/4 - 1,8 = 1 3/8 - 3/4 - 1 8/10 = 1 15/40 - 30/40 - 1 32/40 = 55/40 - 30/40 - 72/40 = 25/40 - 72/40 = -47/40 = -1 7/40