If it's 0.7888888... we can write this as 7.888888.../10=(7+8/9)/10=71/90.
If it's 0.8777777... we can write it as (8+7/9)/10=79/90.
(To find the fraction equivalent to a recurring decimal write the recurring part divided by the same number of 9s. For example, 0.8888... means the recurring part is one digit only so we only need one 9: 8/9. Another example, 0.090909.... this time the recurring part is two digits so the fraction is 09/99 or 9/99=1/11. To get the non-recurring part out of the way, we multiply by as many tens as necessary to put the non-recurring part on the other side of the decimal point. Then we divide by as many tens to make the fraction. So 0.083333... needs to multiplied by 100 to give us 8.333333... 3/9=1/3. 8.3333... is therefore 8+1/3=25/3. Now divide by 100: 25/300=1/12; so 0.083333... = 1/12.)