Hi Abby,
I'm not sure what you've learned yet in school, but the best way to solve this question is by using a system of equations. (So, I'm not sure if you've learned systems yet.) But, I'll help you with solving this...
Let your first equation represent the quantities of the candy bars.
Let your second equation represent the costs of the candy bars.
Let "P" represent peanut bars and let "C" represent chocolate bars.
Your equations would be:
P + C = 17
.69P + .59C = $10.83
I would solve this system by eliminating one of the variables (then, you'll be able to solve for the remaining variable.)
I would eliminate a variable by adding the 2 equations together.
To eliminate a variable, that variable would need to have the same value in each equation, but with opposite signs.
If you multiply the entire first equation by -.69, your new equation would be:
-.69P - .69C = -11.73
So your system now looks like this:
-.69P - .69C = -11.73
.69P + .59C = $10.83
Add the 2 equations together. The "P" variable would be eliminated (-.69P + .69P = 0)
You're left with:
-.1C = -.9
Divide both sides by -.1. You're left with:
C = 9
Plug 9 back into the first equation for the variable C:
P + C = 17
P + 9 = 17
Subtract 9 from both sides:
P + 9 - 9 = 17 - 9
P = 8
So Susan bought 9 chocolate bars and 8 peanut bars.
