24 * 3/8 = 24 : 8 = 3 * 3 = 9
5/6 : 30 = 5/6 * 1/30 = 1/6 * 1/6 = 1/36
1. 20542-687=19855;
2. 19855+8032=27887;
3. 43*17=731;
4. 27887-731=27156;
(50+65)+(220+250)= 115+ 470=585
(220+65)-250= 285-250=38
(50+65)+220= 115+220=335
220-(65+50)=220-115=105
250-(50+65)=250-115=135
2) 1)41/18+52/45=93/63
2)38/45+7 13/18=5 99/031
3) 1) 21/14+8 12/35=3 59/879
2)58/35+7 5/14=33 5/899