Answer: 138
Explanation:
We need to find a number which increased by 3.5 of itself equals 621.
Let that number be x.
x increased by 3.5 of itself equals 621 implies x+ 3.5x = 621.
x(1+3.5) = 621
x(4.5) = 621
x = 621/4.5
x = 138
Therefore the required number is 138.