To write 0.0007716049 as a fraction you have to write 0.0007716049 as numerator and put 1 as the denominator. Now you multiply numerator and denominator by 10 as long as you get in numerator the whole number.
0.0007716049 = 0.0007716049/1 = 0.007716049/10 = 0.07716049/100 = 0.7716049/1000 = 7.716049/10000 = 77.16049/100000 = 771.6049/1000000 = 7716.049/10000000 = 77160.49/100000000 = 771604.9/1000000000 = 7716049/10000000000
so your answer is: 7716049/10000000000