SAT Mathematics Practice Test 3

First, clear the fractions from the given equation by multiplying each side of the equation by 36 (the least common multiple of 4,9, and 12).
The equation becomes 28x−16x=9+15.
Combining like terms on each side of the equation yields 12x=24.
Finally, dividing both sides of the equation by 12 yields x=2.
Alternatively, since

7

9

x−

4

9

x=

3

9

x=

1

3

x and

1

4

+

5

12

=

3

12

=

8

12

=

2

3

the given equation simplifies to

1

3

x=

2

3

.
Multiplying of

1

3

x=

2

3

by 3 yields x=2