Answer:
20 gallons were used from the tank with the octane rating of 80.
Step-by-step explanation:
Given : One tank of gasoline has an octane rating of 140 and another tank of gasoline has an octane rating of 80. To obtain a mixture of 60 gallons with an octane rating of 120.
To find : How many gallons should be used from the tank with the octane rating of 80?
Solution : Let x be the volume of gas whose octane rating is 140 and
y be the volume of gas whose octane rating is 80.
Then, we form the equation as:
(1) 

or
.........[3]
(2) 
Now multiply equation (2) by 4
...........[4]
Subtract (4) from (3)



Put x in equation [4] we get,





Therefore, x=40 and y=20
So, 20 gallons were used from the tank with the octane rating of 80.
I have taken the test and I can confirm that the answer is
B. 15 m, 20 m, and 25 m.
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Answer:
20°
Step-by-step explanation:
The sum of angles in a ∆ = 180°
Therefore,
Use this expression to find the value of x, then find the measure of angle A.

Subtract 20 from both sides


Divide both sides by 20


Find measure of angle A.
Angle A is given as 
Plug in the value of x and solve
