a) $$16 - 10 - 90 : 7 - 5 - 28 = 6 - 90:7 - 5 - 28 \approx -41.86$$
б) $$800 : 25 - 30 - 510 : 10 - 2 = 32 - 30 - 51 - 2 = -51$$
в) $$7 : 5 - 0.2 - 6 + 3.8 : 5 = 1.4 - 0.2 - 6 + 0.76 = -4.04$$
г) $$0.5 - 20 + 2.3 : 4.1 + 5.2 : 0.2 = -19.5 + 0.56 + 26 = 7.06$$
д) $$4 - 2.8 - 7 : 0.4 - 0.01 + 3.3 = -5.8 - 17.5 - 0.01 + 3.3 = -20.01$$
Ответ: a) -41.86; б) -51; в) -4.04; г) 7.06; д) -20.01