Question 74542
1.
When adding fractions we need to make sure they all have the same denominator. To find the common denominator, we need to find the LCM. The LCM is the product of the denominators divided by the GCF. So 7*9=63 and since the GCF is 1 we get 63. The LCM between 63 and 6 is 
{{{(63*6)/3=126}}}
So the LCM is 126 which is our common denominator. 
{{{1/7+7/9-1/6}}}
{{{(18/18)(1/7)+(14/14)(7/9)-(21/21)(1/6)}}}Multiply each term by a form of 1 to get the common denominator.
{{{18/126+98/126-21/126}}}
{{{(18+98-21)/126}}}
{{{95/126}}}



2. 
To solve for b, divide both sides by (1/3h)
{{{V=(1/3)Bh}}}
{{{V/((1/3)h)=(cross(1/3)B*cross(h))/cross((1/3)h)}}}
{{{B=3V/h}}}
So the answer is D.



3.
To find F, plug in c=-5.
{{{-5=(5/9)(F-32)}}}
{{{-5(9/5)=cross(9/5)(cross(5/9)(F-32))}}}Multiply both sides by 9/5
{{{-cross(5)(9/cross(5))=F-32}}}
{{{-9+32=F+cross(-32+32)}}}Now add 32 to both sides
{{{23=F}}}
So the temperature in Fahrenheit is 23 degrees 



4.
If the elevation changes by 486 feet then that means we add 486 feet to the current elevation. So if we're at 780 feet and we add 486 feet we get 1,266 feet.  If our elevation changes by -641 feet, we subtract 641 from our current elevation of 1266. So we get
{{{1266-641=625}}}
Continue this until all the elevation changes are accounted for.
{{{625+96+494=1215}}}
So the final elevation is 1,215 feet.