Firstly, you do 90 - 42 to get the amount of brownies sold, which is 48. Then, you put 42 and 48 into a ratio like 42:48. After that, all you need to do is simplify to get 7:8.
Let's simplify step-by-step.<span><span><span><span>8.9x</span>−5</span>−<span>6.8x</span></span>+8</span><span>=<span><span><span><span><span><span>8.9x</span>+</span>−5</span>+</span>−<span>6.8x</span></span>+<span>8
</span></span></span>Combine Like Terms:<span>=<span><span><span><span>8.9x</span>+<span>−5</span></span>+<span>−<span>6.8x</span></span></span>+8</span></span><span>=<span><span>(<span><span>8.9x</span>+<span>−<span>6.8x</span></span></span>)</span>+<span>(<span><span>−5</span>+8</span>)</span></span></span><span>=<span><span>2.1x</span>+<span>3
The simplified answer is </span></span></span><span><span>2.1x</span>+<span>3</span></span>
it would be covered by tuesday: because if it doubles each day and it is half full on monday it would be double that so it would be 100% 4/4 covered
To find the cross product, you can set this up as a proportion. Please see the attached paper for one of the proportions you could use.
You would then multiply the numbers that are diagonal from each other.
You would have 21(8) = 12x or
168=12x.