Решите ] 2/3-1/5 3/4+1/10 5/8-3/10 2/7+1/3

2/3-1/5=2×5/3×5-3×1/5×3=10/15-3/15=(10-3)/15=7/15
3/4+1/10=3×5/4×5+2×1/2×10=15/20+2/20=(15+2)/10=17/20
5/8-3/10=5×5/8×5-3×4/10×4=25/40-12/40=(25-12)/40=13/40
2/7+1/3=2×3/7×3+1×7/3×7=6/21+7/21=(6+7)/21=13/21