[tex]\longrightarrow[/tex]Let the the number of dimes be x
[tex]\longrightarrow[/tex]So, the number of nickels = x+4
(as the number of nickels is four more than dimes)
Now,
[tex]\leadsto[/tex]Total amount of money= $ 1.25
[tex]\quad[/tex]= 125 cents [tex]\quad[/tex](1 dollar = 100cents)
[tex]\leadsto[/tex]Amount of money in dimes(in cents)
[tex]\quad[/tex]= 10x [tex]\quad\quad\quad[/tex] (1 dime = 10 cents)
[tex]\leadsto[/tex]Amount of money in nickels(in cents)
[tex]\quad[/tex] = 5(x+4) [tex]\quad\quad[/tex](1 nickel = 5 cents)
further,
Total amount of money by nickels and dimes = 125 cents
[tex]\implies[/tex]10x+ 5(x+4) = 125
[tex]\implies[/tex]10x+5x+20 =125
[tex]\implies[/tex]15x + 20 = 125
[tex]\implies[/tex]15x = 105
[tex]\implies[/tex]x = 7
[tex]\bull [/tex]Number of dimes = x = 7
[tex]\bull[/tex]Number of nickels = x+4
[tex]\quad[/tex]= 7+4
[tex]\quad[/tex]= 11
[tex]\\[/tex]
[tex]\green\therefore \quad[/tex]Sophia has 7 dimes and 11 nickels.