You have two gifts to buy. You plan to spend no more than $40 on the two gifts combined. You want to spend at least twice as much on the first gift as on the second gift. Let x be the amount you spend on the first gift and y be the amount you spend on the second gift.

If you want to spend no less than $40, and you want to spend twice as much on the first gift (gift x), you can spend $26 on gift x. On the second gift (gift y), you can spend $13. You will spend a total of $39 on both gifts which is less than $40 and have spend twice as much on the first gift as you did the second ($13 x 2= $26).