"x" represents an unknown number, we know that 70% of x equals 63.
To calculate the percentage of a number you have to multiply the said number by the percentage, in this case, 70%, and divide the result by 100:
So the 70% of x can be calculated as:
You can simplify this expression by solving the division
Then the expression that shows you the relationship is
Using this expression you can determine the value of x, to do so you have to divide both sides of the equal sign by 0.7
The value of x is 90