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formule  1

7 + 3 x 1 = 7 + 3 = 10

7 + 3 x 5 = 7 + 15 = 22

7+ 3  x 6.2 = 10 x 6.2 = 62

7 + 3 x 14 = 7 + 42 = 49

formule   2

( 8 + 3) x 8 = 11 x 8 = 88

( 2 + 3 ) x 2 = 5 x 2 = 10

( 15 + 3 ) x 15 = 18 x 15 = 270

( 0.3 + 3) x 0.3 = 3.3 x 0.3 = 0.99

formule  3

( 5 x 4 - 3 ) x 2  = ( 20 - 3 ) x 2 = 17 x 2 = 34

( 5 x 2 - 3 ) x 2 =  ( 10 - 3 ) x 2 = 7 x 2 = 14

( 5 x 5  -3) x 2 = ( 25 - 3 ) x 2 = 22 x 2 = 44

( 5 x 0  - 3) x 2 =  ( 0 - 3 ) x 2 = - 6