The area of the triangle above will equal one half of a rectangle that is 5 units long and 3 units wide.
The area of the triangle is 7.5 units and the area of the rectangle is 15 units
<span><u>1/3x - 1/2y = 1</u>
At the 'x' intercept, y=0 , and the equation is 1/3 x = 1
Multiply each side by 3 : <em>x = 3 </em> <== the x-intercept
At the 'y' intercept, x=0, and the equation is -1/2 y = 1
Multiply each side by 2 : - y = 2
Multiply each side by -1 : <em> y = -2 </em> <== the y-intercept
</span>
In order to get an 81 average,
the student has to get 81x5=405
71+96+90+73+?=405
330+?=405
405-330=75
he needs to get an 75