[ณ นที]

ข้อ 34) ตอบ 169
Z = 1 =1
Y = 2 =1+1, Y-Z = 1
X = 4 =1+1+2
W= 7 =1+1+2+3 , W-X = 3
V =11 =1+1+2+3+4
U =16 =1+1+2+3+4+5, U-V = 5
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B =1+1+2+3+...+24
A =1+1+2+3+...+25, A-B = 25
A-B+C-D+E-...+W-X+Y-Z = 1+3+5+...+25 = 169