822
Monday = 642, Tuesday = 723, Thursday = ?
The first digit= number of letters, the second digit= formed from the first letter's alphabet order, the third digit= number of vowels
For Monday- 6 letters, M=13=1+3=4, O+A=2--> 642
For Tuesday- 7 letters, T=20=2+0=2, U+E+A=3 --> 723
For Thursday- 8 letters, T=2 as above, U+A=2 --> 822
