If (2 3 5 7)(1 -3 2 -4) = (x y z w), write value of x.

Consider,
(2 3 5 7)(1 -3 2 -4) = (x y z w)
(2 × 1 + 3 × 2 2 × -3 + 3 × -4 5 × 1 + 7 × 2 5 × -3 + 7 × -4) = (x y z w)
(2 + 6 -6 -12 5 + 14 -15 -28) = (x y z w)
(8 -18 19 -43) = (x y z w)
Equating the matrices we get the value of x that is x = 8
Hence x = 8.