Exercise 57 Page 57

This is not the easiest thing to calculate in our heads. Let's solve this equation using a table. In order to choose a good starting point for our table, let's pretend that the equation is 5a=-16. What multiplied by 5 would get us close to -16? -3 or -4 would be equally valid, so let's try those. We should also try one digit less and one digit greater, just to be on the safe side.

Since our equation is 5a-4=-16 and -19<-16<-14, we know that the solution lies between -3 and -2. -3