Exercise 56 Page 57

Consider the given equation. -3+t=19 To solve this equation using mental math we want to think about what it means in words. -3 + t = 19 Add a number to $-3$to be$19$. This can be made easier if we use the Properties of Real Numbers to write an equivalent equation.

-3+t=19

CommutativePropAdd

Commutative Property of Addition

t+(-3)=19

AddNeg

a+(- b)=a-b

t-3=19

This equation can now be read as follows. t -3= 19 Take away3from a number to be$19$. We know that if we take away 3 from 22 we get 19. Therefore, t=22.