7 целых 1/4 х - х = 9 целых 3/8
7 1/4х-х=9 3/8
29/4х-х=75/8
29/4х-4/4х=75/8
25/4х=75/8
х=75/8 : 25/4
х=75/8* 4/25
х=3/2* 1/1
х=3/2=1 1/2