Let x- intercept represents time
Let y-intercept represents population
Let 1990 represent initial year
Points are (0,14.2)(10,12.4)
slope m= 
= 
General linear equation
y= mx+b --------------(i)
here m is slope and b is intercept
plug the 1st point in equation
14.2= -0.018(0) + b
b=14.2
y= 0.018x + 14.2
replace y with p(t) and x with t
p(t) = -0.018t + 14.2
x/.75=x-56/0.4
0.4x=.75x-42
-0.35x=-42
x=120
I set up a proportion in which x=the tank when it is 3/4 full. When the tank is 3/4 full, solving the proportion tells us the x=120 litres. 120/3=40, and 120+40 is 160, showing that a tank completely full would indeed hold 160 litres.
Hope this helps!
<em>Hey</em>
<em>The</em><em> </em><em>value</em><em> </em><em>of</em><em> </em><em>X </em><em>is</em><em> </em><em>3</em><em>5</em><em>°</em>
<em>X</em><em> </em><em>and</em><em> </em><em>3</em><em>5</em><em>°</em><em> </em><em>are</em><em> </em><em>vertically</em><em> </em><em>opposite</em><em> </em><em>angles</em><em>.</em>
<em>Vertically</em><em> </em><em>opposite</em><em> </em><em>angles</em><em> </em><em>are</em><em> </em><em>always</em><em> </em><em>equal</em><em>.</em>
<em>Hope</em><em> </em><em>it</em><em> </em><em>helps</em>
<em>Good</em><em> </em><em>luck</em><em> on</em><em> your</em><em> assignment</em>