Question 290466
This is a word problem with coins.
What do we know ?
There are 30 coins and the  coins are nickels and dimes
so n+d=30
we also know their value.
5n+10d=235
now we have two equations with two unknowns so we can solve it.
n+d=30
5n+10d=235

n=30-d
substitute
5(30-d)+10d=235
150-5d+10d=235
150+5d=235
5d=85
d=85/5
d=17
so n=13
check
5*13+17*10=235
65+170=235
235=235