2x -5 = 2-1
2x -5 +5= 2-1+5
2x = 6
2x/2 = 6/2
x = 3
21 is the only solution of that equation.
If you mean 28 = 7+y then the solution of the equation is y = 21
If you mean: 7x+21 = 105 Then the solution is: x = 12
The solution (not sum) to the equation 21 = 3c + 6 is as follows:21 = 3c + 621 - 6 = 3c + 6 - 615 = 3c3c = 153c/3 = 21/3c = 7
21
12
21
22=7x+1 (take 1 of each side of the equals) 21=7x (divide each side by seven) 3=x (BAM! answer)
-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.
The solution is k = 9.