Răspuns:
abc=398
Explicație pas cu pas:
2+4+6+…..+abc=abc00
notăm abc=2*x
abc00=abc*100
=> 2+4+6+...+2*x=2*x*100
2(1+2+3+....+x)=2*x*100 /:2
1+2+3+....+x=x*100
(1+x)*x/2=x*100
(1+x)*x=x*200 /:x
1+x=200
=> x=199
=> abc=2*199
abc=398
verificare:
2+4+6+...+398=2(1+2+3+...+199)=2*(1+199)*199/2=200*199=39800