On the visible sides of the two cards there are numbers 5 and 12. The sum of the two numbers on the first card

On the visible sides of the two cards there are numbers 5 and 12. The sum of the two numbers on the first card is equal to the sum of the numbers on the second card. The sum of four numbers is 32 Which two numbers are written on the back of the cards.

The numbers on the reverse sides of the cards will be designated: on the first – “A”; on the second – “B”. Let’s write down the condition:

5 + A = 12 + B

5 + A + 12 + B = 32

From the first equality we express “A” and replace it in the second equality:

A = 12 + B – 5 = 7 + B

Replacement:

5 + (7 + B) + 12 + B = 32

2B = 32 – 5 – 7 – 12 = 8

B = 4

Then A = 7 + 4 = 11

Examination:

5 + 11 = 12 + 4

16 = 16 – yes.

5 + 11 + 12 + 4 = 32

32 = 32 – yes.

Answer: numbers on the back: first card: 11; second: 4.