Question

a collection of 30 coins consists of dimes and Nickles the total is 1.80 how many dimes are there

Answer 1

6 dimes and 24 nickels. Use A+b= 30 and 0.05a + 0.10b = 1.80
and add or subtract those two equations then sub in one variable for the other answer.

Answer 2

so
d=number of dimes
n=number of nickles

so
n+d=30

value=1n=0.05 and 1d=0.1
therefor,
value=0.05n+0.1d
value=1.80

1.8=0.05n+0.1d
mltiply by 100 to make easier
180=5n+10d
divide both sides by 5 to simplify
36=n+2d
so we have
30=n+d and
36=n+2d

30=n+d
multiply by -1
-30=-n-d
add to other equation

36=n+2d
-30=-n-d  +
6=0n+d

6=d



answer is 6 dimes