No one is responding because we can't read the problem.
Obviously, there's a typo . . . and it still doesn't make sense.
Find coefficients a1,a2 and a3 such that (1 2 1) = a1V1 + a2V2 + a3V3 . ?
I would guess that the "coefficients": belong to (somehow).
But is a constant.
. . It can not equal a matrix:
Please state the original problem . . . carefully.