Deijah gave isaiah $6.25 in nickels and quarters. if 12 coins were quarters, how many coins were nickels? which equation models this problem?
a) 0.25•12+0.05•n=6.25
b) 0.05n+625=0.25•12
c)25+5n=6.25
d) 6.25+0.05=12•0.25

Deijah has $6.25. 

Now, this 6.25 is comprised of 0.05s and 0.25s. 
We know that there are 12 0.25s.

We now want to know how many remaining 0.05s there are.

Again, we know that the number of 0.05s he has, which is 12, multiplied by 0.05, plus the number of 0.25s he has, multiplied by 0.25, equals 6.25.

Thus, the answer is A, 0.25 x 12 + 0.05 x n = 6.25.