Question

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

Answer 1

X is the number of hours worked as a carpenter
Y is the number of hours worked as a blacksmith

20x + 25y = 690
x + y = 30


I moved the x over in the second equation and solved for
y = 30 - x

I then substituted that in for y in the first equation.
20x + 25y = 690 BECOMES

20x + 25(30 - x) = 690

Distributing:

20x + 750 - 25x = 690

750 - 5x = 690

-5x = -60

x = 12. Thus Giselle worked 12 hours as a carpenter.

Since she worked 30 in total, the other 18 hours (30 minus 12 = 18) must be worked as a blacksmith

Answer 2

Explanation:

Let Giselle worked as carpenter =c hours

and Blacksmith =b hours

c+b=30

c=30-b

20+20 c+25+25 b=690

20 c+25 b=690-45=645

4c+5b=129

4(30-b)+5b=129

120-4b+5b=129

b=9 hours

c=30-9=21 hours