Answer: [tex]420\ \text{d}[/tex]
Step-by-step explanation:
Given : Brian earns P 420 a day working part time at a convenience store.
Let d denotes the number of days.
Then , the amount of money ( in P) he will earn in d days is given by :-
[tex]\text{Amount= Amount per day}\times\text{Number of days}\\\\\Rightarrow\ \text{Amount= 420}\times\text{d}=420\text{d}[/tex]
Therefore, the algebraic expression to represent the amount of money he will earn in 'd' days : [tex]420\ \text{d}[/tex]