( 1/3 + 1/2 ) * x = 3,75.

(1/3+1/2)·х = 3,75                           ( 3,75= 3 целых 75/100= 3 цел 3/4=15/4)

5/6 ·х=3,75    
 х= 3,75: 5/6
 х= 15/4:5/6
 х= 15/4·6/5
 х= 9/2
 х=4,5