Giselle works as a carpenter and as a blacksmith. She earns \$20$20dollar sign, 20 per hour as a carpenter and \$25$25dollar sig
n, 25 per hour as a blacksmith. Last week, Giselle worked both jobs for a total of 303030 hours, and earned a total of \$690$690dollar sign, 690. How long did Giselle work as a carpenter last week, and how long did she work as a blacksmith? Giselle worked as a carpenter for hours and as a blacksmith for hours last week.
A - area of a trapezoid; a, b - two bases. A = h * ( a + b ) / 2 / * 2 ( we have to multiply both sides by 2 ) 2 A = h *( a + b ) 2 A = h a + h b h b = 2 A - h a b = ( 2 A - h a ) / h b = 2 A/h - a Answer: D )
