we will simply subtract 11 from both-side of the equation. That is;
11 + z = 6
Subtract 11 from both-side of the equation
11 - 11 + z = 6 - 11
(On the left-hand side of the equation 11 will be subtracted from 11 which gives zero, thereby leaving us with just z while on the right-hand side of the equation 11 will be subtracted from 6 which will give negative 5)
