So let's start off by declaring both of the unknown variables: the number of sundaes and the number of banana splits. Let us say that:
"b" is the number of banana splits sold
"s" is the number of sundaes sold.
Now that we have our variables, we need to start working on the equations. Our first equation will be:
3b + 2s = 156
This equation takes the unknown number of deserts sold, each respectively multiplied by the amount they sell for to equal the amount made. The second equation will look like this:
s - b = 8
This equation means that there are 8 more sundaes sold than banana splits. Now with both of our equations, we can go ahead and solve the problem.
3b +2s = 156
s - b = 8
Our first step is to take one of the equations and isolate one of the unknown values. The value you choose isn't important, just try and pick the easier one. in this instance, I'll be modifying the 2nd equation.
s - b = 8
+b +b
s = 8 + b
So now that we have "s" isolated, we can say that "s" is equal to "8 + b," and we can take this knowledge and substitute it into the 1st equation (substituting it into the same equation will result in zeroing it out).
3b + 2s = 156
3b + 2(8 + b) = 156
And from here, we go ahead and solve the problem as usual until "b" is isolated.
3b + 2(8 + b) = 156
3b + 16 + 2b = 156
5b + 16 = 156
5b = 140
b = 28
So now we have the total number of banana splits sold! To find "s," just plug in the value for "b" and solve as usual
s - (28) = 8
s = 36
And so our final answer is:
s = 36
b = 28
Phil C.
Actually, if you need a follow-up to my discussion of the set-up, HERE IT IS. Patricia C. has said everything I would have, regarding the "substitution" method, and very nicely, too!02/09/21