645 + 50 = 695
137 + 645 = 782.
The 600 would be represented by 500 (D) plus 100 ( c ). And 40 is made by subtracting 10 (X) from 50 (L). So 645 would be DCXLV.
645
1070
428 + 217 = 645
50-500 usd
Dcxlv dcxlv=500+100+(50-10)+5=600+40+5=645
50- 575 usd
65 + 65 + 65 + 90 + 90 + 90 + 90 + 50 + 50 + 50 + 50 + 50 + 50 + 20 + 20 + 20 + 20 + 20 + 20 + 20 = 995
4.99+2.5+.50+.50=7.49
50 + 50 + 94 + 94 = 288
20 + 50 + 20 + 10 = 50 = 150