Gt-m=8k solve for t how do i solve for t?

An airplane travels at an unknown elevation before it descends 3 miles to an elevation of 15 miles. find the elevation of the plane before its descen.

Out of $20$ creepy-crawly creatures in a room, $80\%$ are flies and $20\%$ are spiders. if $s\%$ of the total legs belong to spiders, what is $s$?

Identify the expression equivalent to 4(x + x + 7) − 2x + 8 − 4 by substituting x = 1 and x = 2.