2,6+12+(−1,22r)=5+2,6−3,22r

r = -3,5

Объяснение:

2,6+12+(−1,22r)=5+2,6−3,22r

2,6+12−1,22r =5+2,6−3,22r

3,22r  −1,22r =5+2,6−2,6-12

2r =5-12

2r =-7

r =-7/2

r =-3,5

Проверка

2,6+12+(−1,22*(-3,5)=5+2,6−3,22*(-3,5)

18,87 =18,87