Divide top and bottom by whatever common factors they have.
Do you mean what equals 220/640 in its lowerst terms If so then it is 11/32
You cannot solve fractions. There may be sums or products containing fractions or equations that can be solved. But fractions themselves cannot.
to put a mixed fraction in lowerst terms you divide it by the greatest common factor.
You cannot solve proper fractions. You may be able to solve problems involving fractions but that is NOT the same thing. Furthermore, the solution methods depend on the problem.
You cannot solve a fraction. You can solve a question about fractions, you can carry out basic operations with fractions, convert them from one form to another but none of these is "solving" them.
the graphs have fractions on the y axis
Not necessarily, but often it is simpler to convert fractions into decimals to solve the equation.
You solve it just like they are proper fractions
That depends what kind of calculation you want to do with the fractions.
You can eliminate the fractions before proceeding to solve the equation to allow for easy factorization.
The hcf is useful in reducing fractions to their lowest terms and the lcm is useful in finding the lowest common denominator of fractions that have different denominators that need to be added or subtracted.
Assuming you want to get rid of the fractions, you can multiply both sides of the equations by the greatest common factor of the fractions. Then you can solve the equation normally.