Question 325326
let one tank hold x gallons
the other tank hold 2x+6 gallons
..
together they hold 45 gallons
..
x+2x+6=45
3x+6=45
add-6 to both sides
3x+6-6=45-6
3x=39
x= 39/3
x=13 gallons 
the other tank will hold 45-13= 32 gallons