Could someone help me understand this math please?

Question

The difference of two positive numbers is 28. One number is 3 times the other. Find the two numbers. 

 

all i got was x-y=28 and 3x+y

 

idk what to do with this :

Answer 1

The first equation is correct, but the second is incorrect.  Let me fix it for your. 

 

3x + y      should be      3y = x

 

 

Next, use the substitution method to get only one equation with one variable.  Substitute the equation I just fixed for you into the difference equation.

 

x - y = 28

 

3y - y = 28

 

 

Now we solve for y.

 

2y = 28

 

   y = 14

 

 

Next, substitute this value of y into the second equation to solve for x.

 

3(14) = x

 

42 = x

Answer 2

The first equation is correct. Good job!

The problem states 'one number is three times the other' could be written x= 3y

 

You can then substitute x= 3y into the first equation x-y=28, which would then be written:

3y - y = 28

2y = 28

y = 14

 

if x= 3y, then x= 3(14)

x= 42

 

Always substitute the answers for x and y back into the original two equations to make sure your answers satisfy both conditions.