On the Left hand side you have x//7 +x/3

To add these fractions (with unlike denominators) find the LCM (Least Common Multiple) and use that as the common denominator.

LCM of 7 and 3 is 21

Write an equivalent fraction using 21 as the denominator. So x/7 becomes 3x/21

and x/3 becomes 7x/21.

Now add 7x/21 +3x/21 because they have the same denominator it is easier to add the numerators 10x/21.

Now you have

10x/21 = 22/14

Multiply both sides by 21

10x = 22/14*21= 33

Divide both sides by 10

x = 3.3

Note on Equivalent Fractions:

how x/7 becomes 3x/21? For this problem we had to bring the denominators in both fractions as 21. So check how many 7s are there in 21 or in other words how many times 7 will divide 21? We know 3*7 is 21. So you have to multiply 7 times 3 to get 21 in the denominator. Because you multiplied the denominator 7 *3, you have to also multiply the numerator x times 3 to get the equivalent fraction.

Hope this helps!