This is an alphanumeric problem. Each letter stands for a different digit.
A quick inspection reveals that T is 1, E is 0, V is even and N is at least 7. Applying this knowledge means a computer search will be much quicker. Below is a BASIC programme (BASIC is a computer language) that solves this puzzle. You don’t need to be a computer programmer to get the idea of how the programme works.
100 FOR V=2 TO 8 STEP 2
110 FOR L=2 TO 9
120 IF L=V THEN 350
130 R=10 – 10*(L/2 – INT(L/2)) – INT(V/2)
140 IF R=V OR R=L OR R=0 OR R=1 THEN 350
150 FOR I=2 TO 9
160 IF I=V OR I=L OR I=R THEN 340
170 TEMP=1000*I + 500*L + 100*R + 50 + V
180 N=INT(TEMP/1000) – INT(TEMP/10000)*10
190 IF N=V OR N=L OR N=R OR N=I OR N<7 THEN 340
200 FOR W=2 TO 9
210 IF W=V OR W=L OR W=R OR W=I OR W=N THEN 330
220 FOR H=2 TO 9
230 IF H=V OR H=L OR H=R OR H=I OR H=N OR H=W THEN 320
240 TWELV=10000 + W*1000 + L*10 + V
250 THIRT=10001 + H*1000 + I*100 + R*10
260 NINET=N*10100 + I*1000 + 1
270 IF TWELVE*5 + THIRT<>NINET THEN 320
280 FOR Y=2 TO 9
290 IF Y=V OR Y=L OR Y=R OR Y=I OR Y=N OR Y=W OR Y=H THEN 310
300 PRINT TWELVE*10, THIRT*10 + Y, NINET*10 + Y
310 NEXT Y
320 NEXT H
330 NEXT W
340 NEXT I
350 NEXT L
360 NEXT V
370 END
The solution is E=0, T=1, R=2, W=3, I=4, Y=5, V=6, L=7, N=8, and H=9. Thus TWELVE x 5 + THIRTY = 130,760 + 194,215 = 848,015 = NINETY.