3) 1/40 + 1/60 = 3/120 + 2/120 = 5/120 = 1/24 (часть)
4) за 24 минуты
1.4х-0.1х-0.28=1.67
1.3х-0.28=1.67
1.3х=1.67+0.28
1.3х=1.95
х=1.95:1.3
х=1.5.
45-8=37