Answer:
David start with $45
Step-by-step explanation:
Let
x ----> the original amount of David
y ----> the original amount of Peter
we know that
David had $20 more than Peter
so
[tex]x=y+20[/tex] ----> equation A
After a Peter lost $10, David has three times as much money than Peter
[tex]x=3(y-10)[/tex] ----> equation B
equate equation A and equation B
[tex]3(y-10)=y+20[/tex]
solve for y
[tex]3y-y=20+30\\2y=50\\y=25[/tex]
Find the value of x
[tex]x=25+20=\$45[/tex]
therefore
David start with $45
