Answer:
Sophie has 12.5 cards
Step-by-step explanation:
Let
x -----> number of cards Sophie has
y -----> number of cards Jackie has
we know that
x+y=30 -----> equation A
y=x+5 -----> equation B
Solve by substitution
Substitute equation B in equation A and solve for x
x+(x+5)=30
2x=30-5
x=12.5 cards
Note I assume the problem was invented without taking into account the result, because the amount of cards should be a whole number
18) (10)7d/10=35(10)
7d/7=350/7
d=50
21) 3/4 w=27
(4/3)3/4 w=27(4/3)
w=36
Hope this helps!
Answer:



Step-by-step explanation:

They wanted to complete the square so they took the thing in front of x and divided by 2 then squared. Whatever you add in, you must take out.

Now we are read to write that one part (the first three terms together) as a square:

I don't see this but what happens if we find a common denominator for those 2 terms after the square. (b/2a)^2=b^2/4a^2 so we need to multiply that one fraction by 4a/4a.

They put it in ( )

I'm going to go ahead and combine those fractions now:

I'm going to factor out a -1 in the second term ( the one in the second ( ) ):

Now I'm going to add (b^2-4ac)/(4a^2) on both sides:

I'm going to square root both sides to rid of the square on the x+b/(2a) part:


Now subtract b/(2a) on both sides:

Combine the fractions (they have the same denominator):

2 / 3 of 4 = ( 2 x 4 ) / 3 = 8 / 3 ;
wouldn't you multiply all three?