Question

Giselle works as a carpenter and as

a
blacksmith.
She earns $20 per hour as a carpenter and $25
per hour as a blacksmith. Last week, Giselle
worked both jobs for a total of 30 hours, and
earned a total of $690.
How long did Giselle work as a carpenter
last week, and how long did she work as a
blacksmith?

Answer 1

she worked as a carpenter for 12 hours

And a blacksmith for 18 hours

Explanation:

B=hours as blacksmith

C=hours as carpenter

20c+25b=690

b+c=30

c=30-b

So we substitute this into the first equation

20(30-b)+25b=690

600-20b+25b=690

5b=90

B= 18

18+c=30

C=12

Answer 2

Explanation:

$20/hr carpenter pay

$25/hr blacksmith pay

Let c = hours working carpentry

Let b = hours working as blacksmith

c + b = 30 {equation 1}

20c + 25b = 690 {equation 2}

In equation 1 solve for one variable in terms of the other.

c = 30-b

Substitute that into equation 2:

20(30-b) + 25b = 690

600 - 20b + 25b = 690

5b = 90

b = 90/5

b = 18 hours working as a blacksmith

c = 30-b = 30-18 = 12 hours as a carpenter