The answer is to your question -20
Slope = (-1-4)/(2+3) = -5/5 = -1
hope it helps
412.638 using expanded form using decimals is :
4 x 100 + 1 x 10 + 2 x 1 + 6 x 0.1 + 3 x 0.01 + 8 x 0.001 Hope this helped you!
Can you put a picture cause that’s a lot to read and remember

Substitute the values. 
Follow PEMDAS and multiply and divide first. 

Continue following PEMDAS and subtract. 