Laura has $18.45 left after buying a shirt for $16.80 and a sweater for $24.75 how much money did laura start with? plz explain

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

3x + 4y = 5 x- 3y = -7 solve by substitution

Me its important ! marge runs an ice cream parlor. her speciality is triple chocolate sundaes. she can prepare 1 sundae every 2 minutes, and she earns $1.20 for each sundae she makes . if she just makes sundaes for a single shift of at most 4 hours and at least 2 hours , which function relates her earnings to the number of minutes she works?