We need to find how much each brother spent.
Josh:
To find how much he spent we use the rule of three:
[tex]\begin{gathered} 20\rightarrow100 \\ x\rightarrow30 \end{gathered}[/tex]then:
[tex]x=\frac{30\cdot20}{100}=6[/tex]Hence Josh spent $6.
Ralph:
To find how much money he spent we divided the $20 by 4, then:
[tex]\frac{20}{4}=5[/tex]Hence Ralph spent $5.
Marcus:
To find how much he spent we use the rule of three:
[tex]\begin{gathered} 20\rightarrow100 \\ x\rightarrow20 \end{gathered}[/tex]then:
[tex]x=\frac{20\cdot20}{100}=4[/tex]Hence Josh spent $4.
Trevor:
The problem already said that he spent $4.50.
Comparing how much each of them spent we conclude that Josh spent the most.