make all bottom same
3/8+4/5
8 and 5 is 40
3/8 times 5/5=15/40
4/5 times 8/8=32/40
15/40+32/40=47/40=1 and 7/40
1 and 9/10+3/4
1 and 9/10=10/10+9/10=19/10
4 and 10 are 20
19/10 times 2/2=39/20
3/4 times 5/5=15/20
38/20+15/20=53/20=2 and 13/20
2/8+6/12
1/4+1/2
4 and 2, common is 4
1/2 times 2/2=2/4
1/4+2/4=3/4