Answer:
Using the ratio and proportion method, we find that on an average 1.875 rooms can be painted per gallon.
Step-by-step explanation:
Concept: Use the method of ratio and proportion. Given that for 2/5 gallons of paint, we can paint 3/4 of rooms. So, for one gallon of paint, divide 2/5 by 3/4.
2/5 gallons of paint = 3/4 rooms
1 gallon of paint = 
rooms
So, on an average they can paint 1.875 rooms per gallon.
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Multply both equations by 2 leaving
x + 2y = 8
x - 2y = -2
Add the equations giving
2x = 6
x = 3
Substitute 3 in the top equation
3 + 2y = 8
2y = -5
y = -2.5
As fraction it would be 6/30 reduced 1/5 and as percentage 20% so 20% of the students were off.<span />
70 x 100 = 7,000
Therefore, 70 hundred is equal to 7 thousands.
Substitute the first equation into the second equation. You will get:
4x - (2x - 5) = 7
Distribute the negative sign into the parenthesis:
4x - 2x + 5 = 7
Simplify
2x + 5 = 7
Subtract 5 on both sides
2x = 2
x = 1
Now, substitute x = 1 into the first equation:
y = 2(1) - 5
y = 2 - 5
y = -3
The solution to the system of equations is (1, -3).
