Besoin De Quelqu'un De Fort

bonsoir

a = 45/14 x 21/135 
a = 945 / 1890
a = 1/2

b = 36/7 : 72/98
b = 36/7 x 98/72
b = 3528/504
b = 7

a = 9x5 / 7x2  x 7x3 /5x9x3
a = 1/7x2 x 7x3/3
a = 1/7x2  x 7
a = 1/2

b = 36/7 x 49x2/ 8x9
b = 36/7 x  49/4x9
b= 9x4 /7 x49/4x9
b = 1/7 x49
b = 49/7
b = 7