Question 23307
1) Solve for f:
{{{(2/f)+t=3/m}}} Subtract t from both sides of the equation.
{{{2/f = (3/m)-t}}} Simplify the right side.
{{{2/f = (3-mt)/m}}} Multiply both sides by f.
{{{2 = f(3-mt)/m}}} Finally, multiply both sides by {{{m/(3-mt)}}}
{{{f = 2m/(3-mt)}}}

2) Calculate f when m=4 and t=3

{{{f = 2*4/(3-4*3)}}}
{{{f = 8/(3-12)}}}
{{{f = 8/-9}}}
{{{f = -8/9}}}