Vivian L. answered • 12/01/13

Tutor

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Microsoft Word/Excel/Outlook, essay composition, math; I LOVE TO TEACH

Hi Nancy;

FIRST EQUATION...P+C+D=30

SECOND EQUATION...P+C=D+6

4P+2C+2D=80

Let's divide both sides by 2...

THIRD EQUATION...2P+C+D=40

Let's begin with the second equation..

P+C=D+6

This is also...

P+C-D=6

Let's add the first equation and second equation....

P+C-D=6

+(P+C+D=30)

2P+2C=36

Let's divide both sides by 2...

P+C=18--------we will use this again below...

The first equation was...

P+C+D=30

Let's substitute P+C with 18...

18+D=30

Let's subtract 18 from both sides...

D=12

Let's return to the third equation...

2P+C+D=40

2P+C+12=40

Let's subtract 12 from both sides...

2P+C=28

Let's subtract formulas...

2P+C=28

-(P+C=18)------from above

P=10

Let's return to the first equation...

P+C+D=30

10+C+12=30

C+22=30

C=8

Let's double check this with the third equation...

2P+C+D=40

2(10)+8+12=40

20+8+12=40

40=40

Nancy L.

12/17/13