Question 7970
All you're doing is trying to isolate the variables from the numbers.  So here it goes:


{{{5d-3=-18}}} , <--add 3 to both sides so that you ONLY have 5d on one side
(5d-3)+3=(-18)+3
{{{5d=-15}}}  <--divide both sides by 5
{{{5d/5}}}={{{-15/5}}}
d=-3


{{{3-4c=-13}}},   <--subtract 3 from both sides 
(3-4c)-3=-13-3
{{{-4c=-16}}}    <--divide both sides by -4
{{{-4c/-4}}}={{{-16/-4}}}
c=4


{{{2x+1=-4+7x}}},  <--subtract 2x from both sides
(2x+1)-2x=(-4+7x-2x)
{{{1=-4+5x}}}   <--add 4 to both sides
(1)+4=(-4+5x)+4
{{{5=5x}}}   <--divide both sides by 5
{{{5/5}}}={{{5x/5}}}
1=x 


-4-5x=2x+10,  <--add 5x to both sides
{{{(-4-5x)+5x=(2x+10)+5x}}}
-4=7x+10  <--subtract 10 from both sides
(-4)-10=(7x+10)-10
-14=7x  <--divide both sides by 7
{{{-14/7}}}={{{7x/7}}}
-2=x


5r+2(r+1)=30, 
5r+2r+2=30
7r+2=30
(7r+2)-2=(30)-2
7r=28
{{{7r/7}}}={{{28/7}}}
r=4


9m-4(m-3)=27
9m-4m+12=27
5m+12=27  <--subtract 12 from both sides
(5m+12)-12=(27)-12
5m=15  <--divide both sides by 5
{{{5m/5}}}={{{15/5}}}
m=3