1 and 3 are the denominators of both the fractions respectively.
Let's convert the unlike fractions into like fractions
Multiples of 1: 1, 2, 3, 4, ..
Multiples of 3: 3, 6, 9, 12, ..
LCM(1, 3) = 3
Now we have to convert the denominators in both the fractions into 3 (LCM of 1 and 3)
5=51=5×31×3=153
and 13 is already in its third form.
∴5+13=153+13
=15+13
=163=x3
⇒x=16