When would you "prefer" solving by substitution? and when would you "prefer" solving by elimination? answer by starting off with "you'd prefer solving by substitution/elimination when.." !

Georgia bought a packge of of 14 dollies to use in her valentines.she used 5/7 of the package to make her in valentines. how many dollies did she have left

Ariel is working at a meat packing plant for 5 nights a week. her regular wage is $11 an hour. she earns tine and a half for any overtime hours. this week she worked 9 hours of over time .how much will ariel earn for overtime this week ?

What is the slope of the line that contains the points (-5, 6) and (14. - 7)?