Hi there! Hopefully this helps!
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<h2 /><h2>Answer: 18</h2><h2>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~</h2><h2 />
First we need to substitute the value of the variable into the expression.
=
.
Now we need to solve
.
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First, calculate 3 to the power of 2 and get 9.

Multiply 2 and 4 to get 8.
Subtract 5 from 8 to get 3.
Multiply 3 and 3 to get 9.
.
<h2>And the answer is, you guessed it, 18!</h2>
Answer:
First brand of antifreeze: 21 gallons
Second brand of antifreeze: 9 gallons
Step-by-step explanation:
Let's call A the amount of first brand of antifreeze. 20% pure antifreeze
Let's call B the amount of second brand of antifreeze. 70% pure antifreeze
The resulting mixture should have 35% pure antifreeze, and 30 gallons.
Then we know that the total amount of mixture will be:

Then the total amount of pure antifreeze in the mixture will be:


Then we have two equations and two unknowns so we solve the system of equations. Multiply the first equation by -0.7 and add it to the second equation:



+

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We substitute the value of A into one of the two equations and solve for B.


Answer:
12
Step-by-step explanation:
the original ratio was 3/5 , so apply that to 20 and 3/5 of 20 is 12
Complete Question
The complete question is shown on the first uploaded image
Answer:
First Question
Option A is correct
Second Question
Option C is correct
Third Question

Fourth Question
So substituting for D in (ABC) D = I


This proof that ABC is invertible
Step-by-step explanation:
From the question we are told that
A , B and C are invertible which means that
exist
Now
From the question
(ABC) D = I
Where I is an identity matrix
Now when we multiply both sides by
we have


Now when we multiply both sides by
we have


Now when we multiply both sides by
we have



So substituting for D in the above equation


This proof that ABC is invertible
40(60/100) 4(6/10) =24/10 = 2.4