Math question....?

Question

Nicole has 25 cds and tapes altogether. When she tries to pair them up, she has 4 cds left over. How many tapes does Nicole have?
&
Anna is twice as old as her brother Dennis, who is 4 years older than their brother Curtis, The sum of their ages is 32 years old. How old is Anna?

I just need to know the equation for those 2 questions and could someone explain how to do it?

Answer 1

is there really 25 cds? cuz that messes up solving the equation:

x = tapes
x+4 = cd's

x + (x+4) = 25
2x + 4 = 25
2x = 21
x= 10.5....?

check: 10.5 + (10.5 + 4) = 25
21 + 4 = 25
25 = 25


A = 2D
D = 4 + C

2(4+C) + (4+C) + C = 32
anna dennis curtis

8 + 2C + 4 + C + C = 32

12 + 4C = 32
4c = 20
c = 5


Curtis is 5
Dennis is 9
Anna = 18

check = 5 + 9 + 18 = 32

Answer 2

Second question:

Anna = 2 X Dennis
Dennis = Curtis +4
Dennis + Anna + Curtis = 32

Substitute all for Curtis:

Curtis + 4 + 2X (Curtis +4) + Curtis = 32
Curtis + 4 + 2Curtis + 8 +Curtis = 32
4 Curtis + 12 = 32
4 Curtis = 20
Curtis = 5
Dennis = 9
Anna = 18

Check (5 + 9 + 18) = 32

The first question:

c=t+4
C+t=24
2t +4 = 24
t=20/2 She has 10 tapes and 14 CDs

if it's 25, then there isn't an even answer

Answer 3

C is number of Cd's, T is number of tapes
C + T = 25 (the total is 25)
C = T + 4 (there 4 more Cd's than tapes)

A is age Anna, D is age Dennis, C is age Curtis
A = 2*D (Anna is twice as old as Dennis)
D = C + 4 (Dennis is 4 years older than Curtis)
A + C + D = 32 (Together they are 32)

Answer 4

i'm not sure about the first question but i figured out the second.

First you have to determine the least known variable. and thats Curtis. so:

Curtis=x

since Dennis is 4 years older than Curtis, you add 4 to the x and that equals Dennis's age:

x+4=Dennis

and Anna is twice as old as Dennis. you multiply 2 to x+4 and that equals 2x+8.

2x+8=Anna

Since the sum of their age equals 32, you add all the variables together and solve for x.

x+x+4+2x+8=32

and once you solve the x, plug in x into 2(x+4) and that equals anna's age.

I hope you understand it

Answer 5

not enough info for the first one - I would just take 4 from 25 (21) and then divide by two - which you cannot do as a whole number.

anna = 2(a=4)
dennis = a+4
Curtis = a

a+a+4 + 2a+8 = 32

add up the 'a's

4a+12 = 32
or 4a=20
a= 5

Curtis is 5
Dennis is 9
Anna is 18

Answer 6

nicole has 9 tapes
anna is 18....dennis is 9 and curtis is 5
i got the answers i just cant think of the equations 4 them srry