3 3/4 x + 1 2/3 = 2 11/12

3 3/4x=2 11/12- 1 2/3 =2 11/12 - 1 8/12 =1 3/12 ; 15/4x= 15/12 ; x=15/12*4/15 ; x=1/3

3 3/4х + 1 2/3 = 2 11/12,
15/4х + 5/3 = 35/12,
15/4х = 35/12 - 5/3,
15/4х = 35/12 - 20/12,
15/4х = 15/12,
х = 15/12 : 15/4,
х = 15/12 * 4/15,
х = 1/3