100 = -(x - 1) + 4(x - 6)

put a -1 where the negative sign is just before the 
first parentheses on the left

Use the distributive principle to remove the parentheses:

100 = -1(x + -1) + 4(x + -6)

100 = -1*x + -1*-1 + 4*x + 4*-6

100 =  -1*x +  1   + 4*x + -24

Rearrange the terms omn the right
to get like terms together:

100 =  -1*x + 4*x + 1 + -24

Use the distributive principle in reverse to
put the x on the outside of parentheses: 

100 =  (-1 + 4)*x + -23

Combine the numbers in the parentheses

100 =       (3)*x + -23

    100 = 3*x + -23

Add +23 to both sides

100 + 23 = 3*x + -23 + 23

    123 = 3*x + 0

    123 = 3*x

Divide both sides by 3

   

   

   

So the solution is x=41.

Edwin