Why is partitioning a directed line segment into a ratio of 1:3 not the same as finding One-third the length of the directed line segment?

Abike shop sells you a bicycle for $63 and a helmet for $21. the total cost is 150% of what the shop spent originally. how much did the shop spend originally? how much profit did the bike shop earn by selling the bicycle and helmet to you ?

Tom had a total of $220 and he spent $35 on a basketball ticket . what percent of his money did he have left?

Ineed in figuring out this problem.