In the student's equation, there are many problems. Nickels are worth 5 cents, represented by .05, not 50 dollars. Also, the coeffient 5 should not be placed there, it belongs with 5(.1), as we already know how many dimes there are. If we were able to make a new one, it would be, 5(.1)+.05n=1.20.
First you have to create a proportion which would look like 25/100 =n/136. to find the answer cross multiply the answer: 100n=25*136 which simplified is: 100n=3400. Now you have to divide by 100 to either side:100n/100=3400/100 and that simplified is n=34 and 34 dollars is your answer