A base-10 integer n = 4d_9 = d0_7, where d represents a single digit. What is the value of n?
4d9 = d07
4 *9 + d = d *7 + 0
36 + d = 7d
36 = 6d
d = 6
4*9 + d = 4* 9 + 6 = 4210
