Answer
$\overline{IV}DLXXVIII$
Work Step by Step
RECALL:
$M=1000
\\D=500
\\C=100
\\L=50
\\X=10
\\V=5
\\I=1$
(1) When a smaller numeral is written before a bigger numeral, the smaller numeral is subtracted to the bigger numeral.
(2) When a bar is written on top, the value is multiplied by 1000.
Note that:
$4578 = 4000+500 + 70 + 8
\\4578= 4000 + 500 + 50 + 10 + 10 + 5 + 1 + 1 + 1
\\4578=\overline{IV}DLXXVIII$
