Bonjour;
-90/7 + 9/35*7/9
= -90/7 +63/ 315
= -90/7 + 7/35
= -90/7*5/5 +7/35
= -450/35+ 7/35
= -457/35
10/9+3 =10/9+ 27/9
= 37/9
-9/5-45/5 = -54/5
(37/9)/ (-54/5)
= 37/9 * -5/54
= -185/ 486
-6/13 *5/5+9/5*13/13
= -30/ 65 + 117/65
= 87/65
(10/7) / (87/65)
= 10/7 *65/87
= 650/ 609