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