Bonsoir,
B=(1/6+1/4)/(-5/4 )
(2/12 + 3/12) /(-5/4)
= (5/12)/ -5/4
=5/12 *-4/5
= -20/ 60 = - 2/6 = -1/3
A= 2/4 - 3/7 x 14/9
2/4 - 42/63
= 2/4 - 2/3
= 6/12 - 8/12
= -2/12= -1/6
B= - 7/8x(2/3-1)
2/3 - 1 = 2/3 - 3/3 = -1/3
7/8 * -1/3 = -7/24
C= 4/5 x 1/4 x 2/5
4/20 * 2/5
= 8/100= 4/50 = 2/25