Question 19353
The main idea here, of course, is to get the variable onto one side of the equation and the numbers onto the other side. The only restriction is, you must use only the valid rules of algebra.

1) {{{3/8 - (1/4)t = (1/2)t- 3/4}}} Add {{{(1/4)t}}} to both sides of the equation. Justification...whatever you do to one side, you must do exactly the same to the other side.
{{{3/8 - (1/4)t + (1/4)t = (1/2)t + (1/4)t - 3/4}}} Now simplify this.
{{{3/8 = (3/4)t - 3/4}}} Add {{{3/4}}} to both sides. Same justification as above.
{{{3/8 + 3/4 = (3/4)t - 3/4 + 3/4}}} Simplify.
{{{9/8 = (3/4)t}}} Finally, multiply both sides by the multiplicative inverse of 3/4...that's 4/3.  Justification...a number multiplied by its multiplicative inverse equals 1 and this leaves you with 1 X t or just t on the right side.
{{{(9/8)(4/3) = t}}} Simplify.
{{{3/2 = t}}} or {{{t = 3/2}}}

2) 
{{{20c + 5 = 5c + 65}}} Subtract 5c from both sides. To get the variables together on one side of the equation.
{{{20c - 5c + 5 = 65}}} Subtract 5 from both sides. To get the numbers onto one side of the equation.
{{{15c = 60}}} Finally, divide both sides by 15.  To get c by itself.
{{{c = 60/15}}}
{{{c = 4}}}

3)
{{{7 - 3r = r - 4(2+r)}}}  Use the distributive property to expand the right side.
{{{7 - 3r = r - 8 - 4r}}} Collect like-terms on the right side.
{{{7 - 3r = -8 - 3r}}} Add 3r to both sides.  To get the variable onto one side of the equation.
{{{7  = -8}}} This can't be true. So the initial equation was inconsistent, i.e., not really an equation.