Giselle works as a carpenter and as a blacksmith. she earns $ 2 0 $20dollar sign, 20 per hour as a carpenter and $ 2 5 $25dollar sign, 25 per hour as a blacksmith. last week, giselle worked both jobs for a total of 3 0 3030 hours, and earned a total of $ 6 9 0 $690dollar sign, 690. how long did giselle work as a carpenter last week, and how long did she work as a blacksmith?

She worked as a carpenter for 12 hours and as a blacksmith for 18 hours.

Assuming you mean she earned $20 as a carpenter and $25 as a blacksmith per hour, with a total of 30 hours for $690,
let c represent carpenter hours and b for blacksmith hours.

20c + 25b = 690
c + b = 30
Subtract b from each side so that c = 30 - b
Plug this value into the first equation

20(30 - b) + 25b = 690
600 - 20b + 25b = 690
600 + 5b = 690
5b = 90
b = 18

To find c, plug this value of b into the other equation
c + 18 = 30
c = 12