I believe it is referred to as The Substitution Method.
Answer:
x > 
Step-by-step explanation:

Add 3 and 1 to get 4.

Use the distributive property to multiply 5 by 9−x.

Subtract 45/5 from both sides.

Since 44/4 and 45/4 have the same denominator, subtract them by subtracting their numerators.

Multiply both sides by -4/5, the reciprocal of -5/4. Since -5/4 is negative, the inequality direction is changed.

Multiply -1/4 times -4/5 by multiplying numerator times numerator and denominator times denominator.


Answer:
x=8a
Step-by-step explanation:
(3/a) x - 4 = 20
add 4 to both sides
(3/a) x = 24
Divide by 3/a
x = 24 / (3/a)
Use KCF (keep change flip)
x = (24/1) x (a/3)
x = 24a / 3
simplify
x = 8a
Answer:

Step-by-step explanation:
<h2><u>Fractions </u></h2>
since
has been completed
the remaining would be :

since <em>denominators are the same </em>
= 
= 
<u>the fraction of the race that is remaining is 3/8</u>