65 is equal to 26% of the total number of questions so:
65 / total number of questions (x) is equivalent to 26 / 100
(65 and 26 are a fraction of the whole thing. it doesn't matter whether they go on the numerator or denominator, as long as they are either both on one or the other)
65/x = 26/100
you can simplify this into
26x = 6500
/26 /26
then you divide by 26 on both sides to isolate the variable
