John sold 10 hamburgers and 14 cheeseburgers.
Step-by-step explanation:
Given,
Cost of one hamburger = $3
Cost of one cheeseburger = $3.50
Total burgers sold = 24
Total revenue earned = $79
Let,
Number of hamburgers sold = x
Number of cheeseburgers sold = y
According to given statement;
x+y=24 Eqn 1
3x+3.50y=79 Eqn 2
Multiplying Eqn 1 by 3

Subtracting Eqn 3 from Eqn 2

Dividing both sides by 0.50

Putting y=14 in Eqn 1

John sold 10 hamburgers and 14 cheeseburgers.
Keywords: linear equation, elimination method
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Answer
Elena must have substracted 1/2x from both sides of the equation.
Lin must have multiplied both sides of the equation by 2
Explanation
The equation given is

For Elena to have arrived at

Then Elena must have substracted 1/2x from both sides of the equation.
That is;

For Lin to have arrived at

It shows Lin must have multiplied both sides of the equation by 2
That is;
He needs 1140 cups of sugar. (total # of cups of sugar) = 114c
Answer:
7w - 3(4w + 8) = 11
Distribute.
-5w-24=11 Combine like terms on the left side.
-5w=11%2B24 Add 24 to both sides.
-5w=35 Combine like terms on the right side.
w=%2835%29%2F%28-5%29 Divide both sides by -5 to isolate w.
w=-7 Reduce.