Given:
a.) Jeremy earns $195 for 3 days of work.
To be able to determine how much will he earn if he works 12 days, we will be using ratios and proportions.
Let,
x = his earnings if he works for 12 days.
[tex]\text{ 195 : 3 = x : 12}[/tex][tex]\text{ 195 : 3 = x : 12 }\rightarrow\text{ }\frac{\text{ 195}}{3}\text{ = }\frac{\text{ x}}{12}[/tex][tex]\frac{\text{ 195}}{3}\text{ = }\frac{\text{ x}}{12}[/tex][tex]\text{ (195)(12) = (x)(3)}[/tex][tex]\text{ 2,340 = 3x}[/tex][tex]\text{ }\frac{\text{2,340}}{3}\text{ = }\frac{\text{3x }}{3}[/tex][tex]\text{ 780 = x}[/tex]Therefore, he'll earn $780 for working 12 days.