Question 354238
x+y=5 or x=5-y
7x+5y=31
7(5-y)+5y=31
35-7y+5y=31
-2y=31-35
-2y=-4
y=-4/-2
y=2 sedans are used.
x=5-2=3 vans are used.
Proof:
7*3+5*2=31
21+10=31
31=31