Question 343865
Bring the multiplier inside the parentheses and multiply everything inside by it.
{{{0.5(12x+80)=(0.5(12x)+0.5(80))=(6x+40)}}}
It's that simple.
{{{2(x+y+z+13)=(2x+2y+2z+26)}}}
OK?
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Fractions, to add or subtract you need a common denominator.
Quickest way is to multiply the two denominators you have together. 
{{{1/3-2/9}}}
You can use a common denominator or {{{3*9=27}}}
{{{(1/3)(9/9)=9/27}}}
{{{(2/9)(3/3)=6/27}}}
So then
{{{1/3-2/9=9/27-6/27}}}
{{{1/3-2/9=(9-6)/27}}}
{{{1/3-2/9=3/27}}}
{{{1/3-2/9=1/9}}}
If you don't use the lowest common denominator (LCD), you will have to simplify your final answer. In your case {{{9}}} was the LCD.
Another example,
{{{3/8+1/5=(3/8)(5/5)+(1/5)(8/8)}}}
{{{3/8+1/5=15/40+8/40}}}
{{{3/8+1/5=23/40}}}
In that case, 40 was the LCD.
OK?