bonjour
A = ( 2/7 - 3/5 ) x ( 1/5 - 9/7)
= ( 10/35 - 21/ 35) x ( 7/35 - 45/35)
= - 11 /35 x - 38/35
= - 49/35
= - 7 / 5
B = 2/7 - 3/5 x 1 /5 - 9 /7
= 2/7 - 3 /25 - 9 /7
= 50/175 - 21/175 - 225/175
= - 196/25
C = ( 1/9 - 3 /4) : ( 8/9 + 5 /4 )
= ( 4/36 - 27/36 ) : ( 32/36 + 45/36)
= - 23/36 : 77 /36
= - 23 /36 * 36/77
= - 828 / 2 772
= - 23/ 77
d = 1/9 - 3/4 : 8/9 + 5 /4
= 1/9 - 3/4 * 9/8 + 5 /4
= 1 /9 - 27/32 + 5 /4
= 32/288 - 243/288 + 360/ 288
= 149/288
