Question

In a two-digit number the tens digit is four less than the units digit. Seven times the tens digit plus five times the units digit is equal to 56. Find the digits.

Answer 1

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Answer:

37

Explanation:

Let our number be “ xy ”

the tens digit is four less than the units digit means y-4=x

Seven times the tens digit plus five times the units digit is equal to 56 means

7x+5y=56

now we have to solve the system:

y-4=x (1)

7x+5y=56 (2)

(1) ⇒ y=4+x

Then we substitute y by 4+x into the second equation like this:

7x+5(x+4)=56

⇔ 7x+5(x+4)=56

⇔ 12x+20=56

⇔ x = 3

now using equation (1) we get : y=3+4 = 7

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