SAT Mathematics Practice Test 5

Use substitution to create a one-variable equation that can be solved for x. The second equation gives that y=2x. Substituting 2x for y in the first equation gives

1

2

(2x+2x)=

21

2

. Dividing both sides of this equation by

1

2

yields to (2x+2x)=21. Combining like terms results in 4x=21. Finally, dividing both sides by 4 gives x=

21

4

=5.25.Either

21

4

or 5.25 can be gridded as the correct answer.