Answer:
D. $680
Step By Step Explanation:
100 pages are typed. Each page coast $5 to type.
100 x 5 = 500
40 pages are revised once. It costs $3 to revise a page once.
40 x 3 = 120
10 pages are revised twice. It costs $3 to revise a page once so it will cost $6 to revise it twice
10 x 6 = 60
To find the total cost we add all the amounts together 
500 + 120 + 60 = 680
The final answer is $680
 
        
             
        
        
        
Sorry about my first answer then it would 20% because if you take 30 and divide 20% you'll get 6 so again sorry I was wrong 20 percent though is right.
        
             
        
        
        
basically you treat y like a number and not a variable
Answer:
a is 4 
b is 2y
c is -10y²+9
discriminant is 4(41y²-36)
Step-by-step explanation:
4x²+2xy-10y²+9=0
rewrite in standard form of a quadratic equation like ax² + bx + c = 0
4x²+2yx-10y²+9=0
basically you treat y like a number and not a variable
a is the number with the x²
right away we know a is 4 because of 4x²
b is the one with x so in this formula b is 2y
c is the number without the x which in this case is -10y²+9
discriminant is 
b² - 4ac 
(2y)²- (4)(4)(-10y²+9)
4y²-(16)(-10y²+9)
4y²-(16)(-10y²+9)
4y²+160y²-144
164y²-144 = 
4(41y²-36)
 
        
             
        
        
        
Answer:
3^-5 or 1/3^5(b)
Step-by-step explanation:
3⁴•3^-9
When bases are same powers are to be added
So the above expression becomes
3^4+(-9)
3^4-9
3^-5