(7 * 4 + с) - (3с - 5) = 28 + с - 3с + 5 = 33 - 2с,
при с = 3/4: 33 - 2 * 3/4 = 33 - 3/2 = 32 2/2 - 1 1/2 = 31 1/2
( 7×4+с )-( 3с-5 ) при с=3/4
28+с-3с+5=33-2с=33-2×3/4=132/4-8/4×3/4=132/4-24/4=108/4=27