x + 6 + 2x = 15
x+2x+6= 15 ( combine like terms)
3x+6= 15
move +6 to the other side
sign changes from +6 to -6
3x+6-6= 15-6
3x= 15-6
3x= 9
divide both sides by 3 to get x by itself
3x/3= 9/3
Cross out 3 and 3 , divide by 3 and then becomes 1*1*x= x
x= 9/3
Answer: x= 3
