Alright, we're dealing with a few values here, so let's give them some labels to save us some trouble down the road. We'll call the number of messages sent by Maria <em>m</em>, the number sent by Bill <em>b</em> and the number sent by Change (is that a real name?) <em>c</em>. We don't know exactly what each number is, but let's take a look at what information they do give us.
Change sent 2 times as many messages as Bill, or, using our variable for Change and Bill:

We're also given that Maria sent 7 messages more than Bill, which we can represent with:

Notice that <em>m</em> and <em>c</em> are both in terms of <em>b</em>. We can use this for our next step. We're given at the beginning that together, Maria, Bill, and Change sent 71 messages over the weekend. As an equation using all of our variables, this translates to:

Since <em>m </em>and <em>c </em>are both in terms of <em>b</em>, we can substitute those expressions in and solve for <em>b</em>:

Now that know that Bill sent 16 texts, we can find the numbers for Change and Maria:

So,
Bill sent 16 texts, Maria sent 23, and Change sent 32.
Answer:
Mark has 13 marbles
Don has 40 marbles
Step-by-step explanation:
Let the number of Mark's Marbles = M
Let the number of Don's Marble = D
D = 1 + 3M - - - - (1) (Don has 1 more than 3 times the number of marbles Mark has)
D + M = 53 - - - - - (2) (total number of marbles is 53)
puttin the value of D from equation (1) into equation (2)
(1 + 3M) + M = 53
1 + 3M + M = 53
1 + 4M = 53
4M = 53 - 1 = 52
4M = 52
M = 52 ÷ 4
M = 13
finding D by putting the value of M (M = 13) into equation 1
D = 1 + 3M - - - - (1)
D = 1 + 3 (13)
D = 1 + 39
D = 40
∴ Mark has 13 marbles
Don has 40 marbles
Answer:
-11
Step-by-step explanation:
-20-(-9)= -11
First terms answer is=39x+39
Second term answer is=90x+15
Check it out how I solved and your welcome:D
Answer:
1 stack of 60
2 stacks of 30
3 stacks of 20
4 stacks of 15
5 stacks of 12
6 stacks of 10
60 stacks of 1
30 stacks of 2
20 stacks of 3
15 stacks of 4
12 stacks of 5
Prime Factorisation

Step-by-step explanation:
To find the number of stacks you can make just divide the total by the size of the stacks. This also works in reverse.
To find the prime factorisation you just find the factors of the number by dividing it by the largest prime possible.