Well basically what you have to do is multiply and it'll be like this (2/3)x2 and exactly like that you'll get 1.333... but then when you change into a fraction you will end up getting 4/3 (four thirds) i hope this helps! ^.^
It would be $2.25
if each student pays one more penny than the last one the penny count would be up to 150 pennies times the number of student which is 150 so multiply and add your decimal