so Regina has 120 coins=total
120=total
we will use q=number of quarters and d=number of dimes
120=d+q
she has 10 more dimes than quarters
d=q+10
so if we susitute this into the equation then we get
120=(q+10)+q
add like terms
120=2q+10
subtract 10 from both sides
110=2q
divide both sides by 2
55=q
she has 55 quarters
subtitute into second equation
d=10+55
d=65
dimes=65
quarters=55
