5 balloons = 1/8 of a heart

____ balloons = 1/4 of a heart

10 balloons because 5 balloons are 1/8 of a heart and 1/4 is double of 1/8 because 1/4=2/8 and 1/8+1/8 is 2/8 so you just have to double 5 and your answer is 10 balloons!