Start by distributing the 6 through the parenthses on the left side.
So we have 6x + 24 = 30.
Solving from here, I would subtract 24 from both sides to get 6x = 6.
Finally, dividing both sides of the equation by 6, we have x = 1.
Perimeter is the sum of all outside dimensions:
5 + 3 + 1 + 2 + 4 + 5 = 20cm
Area = (5 x 5) - (2*1) = 25 - 2 = 23 cm^2
Let n be the amount of 80% solution; and 150-n be the amount of 20% solution. Then:
.8n+.2(150-n)=.6(150)
.8n+30-.2n=90
.6n=60
n=100
150-n=50
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