Take note that they spent $18 afterwards having $28 on the card so they're spending money off the card so...
x-18=28
would be the equation for this and to solve do the following.
First add 18 to both sides making the equation.
x=46
-3x-12> 8x + 21
+12 +12
-3x > 8x + 33
-8x -8x
-11x > 33
————-
-11
x < -3
I moved the real numbers to one side and and the variable to the other side to solve for the inequality
I also remembered somewhere that if you divide by a negative number the inequality sign switches.
Bring the 3 to the other side, which makes 11-3 = 8
divide the whole equation by 2, which makes it Root (3x/5) = 8/2
square the whole equation which gives
, 3x/5 = 16
Multiply the equation by 5 which makes it, 3x = 80
finally divide the equation to find x, x= 80/3
