Abikini and sunglasses cost 110 $ in total. the bikini costs 100 $ more than the glasses. how much do the sunglasses cost?

You can solve this by setting up a system of equations. Let b represent the bikini and s represent sunglasses, then write two equations that go with the situation.

b + s = 110
s + 100 = b

To make this easier, I am going to solve the first equation for b and then set the two b values against each other in an equation.

b + s = 110        Subtract b from both sides
      b = 110 - s   

Now, set the two s values equal to each other and solve for b.

110 - s = s + 100         Add s to both sides
110 = 2s + 100            Subtract 100 from both sides
10 = 2s                        Divide both sides by 2
5 = s

Since s = 5, we know that the sunglasses are $5.