Bonsoir,
A=
5/3 -( 3/5 *2/2 +7/10)
=5/3 -( 6/10 +7/10)
= 5/3 -( 13/10
= 5/3 -13/10
= 5/3 * 10/10 - 13/10 * 3/3
= 50/30 - 39/30
= 11/30
B=
(7/6 * 9/9 - 4/9 * 6/6) -( -7/3)
= 63/54 - 24/ 54) +7/3
= 39/54 +7/3
= 13/18 +7/3
= 13/18 + 7/3 *6/6
= 13/18 +42/18
= 55/18