the sum of 2 numbers is 78 the first number is 3 more than 4 times the second number.

Question

in an ordered pair, what are the two numbers

Answer 1

Here's what we know:

a + b = 78 (together, the numbers equal 78)

a = 3 + 4b (the first is 3 more than 4b)

 

Since we have a value for a variable, we can use substitution here:

4b + 3 + b = 78

5b + 3 = 78

Subtract 3 from both sides:

5b = 75

Divide both sides by 5:

b = 15

 

Now that we know b, we can solve for a:

a = 4 * 15 + 3

a = 60 + 3

a = 63

 

Check:

63 + 15 = 78

78 = 78

 

so the answer is (63, 15)

Answer 2

Do the formula:

78 = A + B

A = 4B + 3

 

Solve for B:

78 = A + B

78 = (4B +3) + B

78-3 = 4B + B

75 = 5B

75/5 = B

15 = B

 

Substitute B in the original formula and solve for A:

 

78 = A + B

78 = A + 15

78 -15 = A

63 = A

 

Then :

78 = 63 + 15