bonjour
a) 3/7 + 15/7 x 3/2
= 3/7 + 45/14
= 6/14 + 45/14
= 51/14
b ) 9/5 x ( 1/4 - 5/12)
= 9/5 x ( 3/12 - 5/12)
= 9/5 x ( - 2 /12 )
= - 18/60
= - 3/ 10
c ) ( 3/8 + 7/5) : ( 9/4 - 5/3)
= ( 15/40 + 56/40) : ( 27/12 - 20/12)
= 71/40 : 7/12
= 71/40 x 12/7
= 852/280
= 213/70