On the first day, he went 32 km, the second day he traveled 16 km, and the third day he traveled 24 km.
Let x be the amount traveled the first day. The second day he went "twice less," or half as much, so 1/2x. the third day, he went 1/2 of the previous two days' total:
1/2(x+1/2x) = 1/2(3/2x) = 3/4x.
Adding these three together, we have:
x+1/2x+3/4x = 72
Find a common denominator. 4 is the first thing 2 and 4 will both divide evenly into:
4/4x + 2/4x + 3/4x = 72
9/4x = 72
Divide both sides by 9/4:
9/4x ÷ 9/4 = 72 ÷ 9/4
x = 72/1 ÷ 9/4
x = 72/1 × 4/9
x = 288/9
x = 32
The first day was 32; half of that makes the second day 16; the total of those two is 48, and half of that is 24.
