20) 1,5-4r+0,5-(-r) +(2,5-16r) + 26r

Решение: \[1.5 - 4r + 0.5 - (-r) + (2.5 - 16r) + 26r = 1.5 - 4r + 0.5 + r + 2.5 - 16r + 26r = (1.5 + 0.5 + 2.5) + (-4 + 1 - 16 + 26)r = 4.5 + 7r\] **Ответ: 4.5 + 7r**