solving equations for a variable

[degi]

I'm so frustrated with this!
Can someone please help me with the following problems:
1.) S=L(1-r), solve for r
2.) S= lw + wh + lh, solve for w
*thats a lowercase "L", not a 1 in question #2

thank you so much in advance for n e one who replies

 

[Ruthie]

1.) S=L(1-r), solve for r

First, multiply out L(1-r) to 1L-Lr. So S=L-Lr. Subtract L from both sides. You get S-L=-Lr. Divide both sides by -L. You get S/-L - L/-L=r. Finally, I get r=-S/L + 1.

2.) S= lw + wh + lh, solve for w

S-lh=lw+wh
S-lh=w(l+h)
S/l+h -lh/l+h =w

 

[degi]

thanks for your help, it didn't even cross my mind to use those techniques!
~degi

 

[Denis]

1.) S=L(1-r), solve for r

S/L = 1-r : divide by L

r = 1 - S/L

r = (L - S) / L

2.) S= lw + wh + lh, solve for w

wl + wh = S - lh

w(l + h) = S - lh

w = (S - lh) / (l + h)