A variable is an unknown or an assumed value of any thing till it is known or it is solved..

A variable is any value varying.

A fixed value is a constant or a known value.

An expression is a mathematical operation or operations ( like addition, subtraction, multiplication, or division , powers, roots, factorials or any defined compositions) etc on numbers or variables.

Here between the number cents and 5 quarters we can establish a relation:

Let 5 quarters be equal to x cents.

So x = 5quarters..........(1) is the relation or equation.

x is the variable. 5quarters is the known value.

x can be any thing for which the relation is true or not true.

We know 1 quarter = 25 cents. So ,

x cents = 5*25cents , here 5*25 cents is an expression. So,

x cents = 5*25cents.

x cents = 125 cents.

x = 125. So x = 125 is the only value for which reation or equation at (1) is true or holds good. (For any other value of x the relation does not hold good. Or the relation is not true for values other than 125.)

The value in cents of 5 quarters would be;

Since 1 quarter is 25 cents

and 1 nickel is equal to 5 cents

To find the value of cents in 5 quarters you would multiply

5 cents times 25 cents so it would equal 125 cents

value of 1 quarter = 1/4

value of 5 quarters = 1/4 * 5 = 5/4

Now we'll convert it to percentage,

to do this we multiply it with 100% So,

5/4 * 100% = 125%