Answer :
[tex]x-\ number\\\\
3x-10=x+4\ \ \ | subtract\ x\\\\
2x-10=4\ \ \ | add\ 10\\\\
2x=14\ \ \ | divide\ by\ 2\\\\
x=7\\\\
Number\ is \ 7.[/tex]
The variable is "the number". To make it easier to write the equation
and work with it, let's call the variable 'M' for 'Mystery number'.
3 times the number is 3M .
-- 10 less than that is 3M-10 .
-- the number plus 4 is M+4 .
The question says that these two things are the same.
So ...
3M - 10 = M + 4
Subtract 'M' from each side: 2M - 10 = 4
Add 10 to each side: 2M = 14
Divide each side by 2 : M = 7