If

is invertible, then we can simply choose

because for any invertible matrix

by definition we must have

.
We have

, as

which means

is non-singular and has an inverse. The inverse itself would be
I know that x=9 not sure the rest but you could ask a tutor
well let's round. 90= 100, 75=80 that is how I face it. now 80 is 1/5 of 5/5= 100. so as a (%) we would sort it like:::: it is 80% out of +100 so he must have grown around 13%-16% due to him being 75kg in the past.
Answer: -5+8 because the difference (-) of -5 and 8 is 8 - (- 5) which can also be expressed as -5+8. All that matters is that 5 stays negative and 8 stays positive.
Company A pays $5500 more than B in year 10