Bread and sugar cost 110 together, bread cost 100 more than sugar, how much does sugar cost?

First write an equation system based on the problem

We can write " Bread and sugar cost 110 together" as

∴ b + s = 110

We can write " bread cost 100 more than sugar" as

∴ b = 100 + s

Second, solve the equation system by subtitution method

Subtitute b with (100+s) in the first equation, and we'll find the value of s

b + s = 110

(100 + s) + s = 110

100 + 2s = 110

2s = 110 - 100

2s = 10

s = 10/2

s = 5

The cost of the sugar is 5