7+4+3+6=? 7+4+3+6=\text{?} 7+4+3+6=?
To make solving the exercise easier, we try to add numbers that give us a result of 10.
Let's keep in mind that:
7+3=10 7+3=10 7+3=10
6+4=10 6+4=10 6+4=10
Hence we obtain a more manageable exercise to solve:
10+10=20 10+10=20 10+10=20
20