Fact Families

This is an introduction to algebra. Fact families show four different ways to solve the same problem.

Given: z + 15= 35
FF: 15+z=35
       35-z=15
       35-15=z
          z=20
**Start with just switching the two addends z and 15
**Any other way to add? Nope!
**Now read the equation backwards and replace the = with a - 
    (35-z=15)
**Since 35 is our largest amount, our last family "member" is to subtract 15 from 35 and ultimately get our answer


Given: 95-y=40
FF: 95-40=y
      y+40=95
      40+y=95
       y=55

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