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.
Answer:
x = 15
Step-by-step explanation:
The right angle is formed at at the tangent line and the radius
So to solve for the missing angle we can solve for x using the Pythagorean Theorem
The Pythagorean theorem states that the sum of the two legs squared equal the hypotenuse squared
Knowing this we can create an equation to solve for x

now we solve for x

So we can conclude that x = 15
A constant in an algebraic expression is defined as a term that does not change during the expression, so, in other words, a term that does not have a variable in it. so the constants are
12
-3.7
1/3
A. -12, -7, -2, 3, 8
B. 3, 2, 1, 0, -1