3.88888=3.88888/1=38.8888888
so lets ssay our repeating decimal = a fraction x
x=3.888 is true
multiply by 10
10x=38.8888
now subtract fir frist eqation from second
10x-x=38.8888-3.888888
9x=35
divide both sides by 9
x=35/9
x=3 and 7/9
anser is 3.88=3 and 7/9