If (begin{pmatrix} 3 & 2 \ 7 & x end{pmatrix} begin{pmatrix} 2 \ 3 end{pmatrix} = begin{pmatrix} 12 \ 29 end{pmatrix} ), find x.
-
A.
5 -
B.
6 -
C.
7 -
D.
8
Correct Answer: Option A
Explanation
(begin{pmatrix} 3 & 2 \ 7 & x end{pmatrix} begin{pmatrix} 2 \ 3 end{pmatrix} = begin{pmatrix} 12 \ 29 end{pmatrix})
(begin{pmatrix} 3 times 2 + 2 times 3 \ 7 times 2 + x times 3 end{pmatrix} = begin{pmatrix} 12 \ 29 end{pmatrix})
(implies 14 + 3x = 29 )
(3x = 29 – 14 = 15)
(x = 5)