The key to math is to master the usage of math language in calculus and matrix and statistics.

practice to be very proficient in converting back and forth the equation system and matrix form.

If given this form

Learn to write into both equation system and then matrix form as

More practice is to change basis skillfully:

The vector space of all polynomials in x of degree less or equal to 2 has a basis of 1, x, x^2, let w1, w2, w3 be a different basis of polynomials whose values at x=-1, 0, 1 are given by below

So to write in matrix for converting/expressing w1, 2, 3 in 1, x, x^2 system is

Reversely do the inverse: