Respuesta :

Creati
Hiya!

Switch the equation around:

2r + 7 = 13 ⇒ 13 - 7 = 2r

The sign changes when moved to the other side( + to -)

13 - 7 = 6

[tex] \frac{6}{2} = \frac{2r}{2} [/tex]

r = 2