1. а. 3/4+1/8=3×2/4×2+1/8=6/8+1/8=6+1/8=7/8
б.11/15-7/20=11×4/15×4-7×3/20×3=44/60-21/60=44-21/60=23/60
в. 5/4×2/3=5×2/4×3=10/12=5×2/6×2=5/6
г. 3/20÷9/10=3/20×10/9=3×10/20×9=30/180=1×30/6×30=1/6
д. 2 2/5+3 1/6=2×5+2/5+3×6+1/6=12/5+19/6=12×6/5×6+19×5/6×5=72/30+95/30=72+95/30=167/30÷17+5×30/30=5 17/30
е. 5 2/3-2 3/4=5×3+2/3-2×4+3/4=17/3-11/4=17×4/3×3-11×3/4×3÷68/12-33/12=68-33/12=35/12=11+2×12/12=2 11/12