Bonjour;
1)
7/9 -10/270
= 7/9 -1/27
= 7/9*3/3 -1/27
= 21/27 -1/27
= 20/27
2)
(3/8 *6/6 -5/6 *8/8) *12/11
= (18/48 - 40/48)* 12/11
= -22/48 *12/11
= -11/24 *12/11
= - 12/24 = -6/12 = - 3/4
3)
(3/7*3/3 -20/21) /3
= (9/21 -20/21) /3
= (-11/21 )/3
= -11/21 *1/3
= -11/63
4)
(3/4*3/3 -7/6*2/2) * ( 2/5*7/7 -2/7*5/5)
= (9/12 - 14/12) * 14/35 - 1035)
= -5/12 * 4/35
= -1/12 * 4/7
= -1/3 * 1/7
= -1 21
