Hello....I was helped on this question earlier, but I don't understand why we divide by 2? Please help, please see the below:
The president will order 5 turkey sandwich combos and 7 steak lunches and spends $124.00. The other president will get 10 turkey combos and 5 steak combos for $140.00. How much is a turkey sandwich combo? Write a system of equation.
5x + 7y = $124.00
10x + 5y= $140.00
???
Algebra - Reiny, Sunday, December 11, 2016 at 11:28pm
After a proper definition of your variables, your system is correct
to solve, how about multiplying the first by 2, and then subtracting them ?
I am sure you can take over from here
I divided the 2nd equation by 2 to get the x terms to be both 5x
Are you not familiar with the method of elimination?
Just like we can multiply each term of an equation by some number, we can also divide each term by some number without changing the value of the equation.
(basic rule of equations: whatever I do to one side, I must do to the other side)
So 5x+7y=124 ---> 10x + 14y = 248
2nd equation : 10x + 5y = 140
now subtract them:
9y = 108
y = 12
sub back into 5x+7y = 124
5x + 84 = 124
5x = 40
x = 8
so the turkey costs $8.00 and the steak sandwich costs $12
check:
sub those values into both equation.
It works!