Bonjour;
A=
21/8 -15/80
= 21/8 *10/10 -15/80
= 210/80 -15/80
=195/80
= 39/16
B=
1/2+45/210
= 1/2 + 9/42
= 1/2 + 3/14
= 1/2*7/7 +3/14
= 7/14 +3/14
= 10/14
= 5/7
C=
15/4 +5/12*9/10
= 15/4 +45/120
= 15/4 + 3/8
=30/8+3/8
= 33/8
D=
45/10-7/10
= 38/10
= 19/5