Answer
$a.\quad 0.49x$
$ b.\quad$ No, the computer is selling at $ 49\%$ of its original price.
Work Step by Step
$a.$
$(x-0.3x)-0.3(x-0.3x)=(x-0.3x)(1-0.3)$
$=(0.7x)(0.7)$
$=0.49x$
$b.$
Using the result of part a,
$0.49=49\%,$
We conclude that the computer is selling at $ 49\%$ of its original price.
