120 - 90x = 210
-16
n + 13 = 21. n = 21 - 13
To find what is divided by what equals 21, you can express it as an equation: ( x \div y = 21 ). This means that ( x = 21y ). For example, if you choose ( y = 1 ), then ( x = 21 ); or if ( y = 3 ), then ( x = 63 ). There are infinitely many pairs of numbers that satisfy this equation.
21
It is an equation and the value of x is 7
21
12
-16
n + 13 = 21. n = 21 - 13
3, 7, 21. 3x7 is the only equation that equals 21, and so these are the only factors of 21.
32
21
It is an equation and the value of x is 7
9+12
5
21 is the only solution of that equation.
21