90-40
=50(alternate angles are equal
Well here is how you do it. you take 84 and estimate the ones place and do the same with 18. since 18 has a big number above 5 or more we raise the score. not to 19, but 20. The 4 in 84 is lower so it stays the sames. we don't keep it as 84 we change the number by taking out 4 and placing a zero. Now all we need to do is do the math. 80 - 20 = 60.
Hope it helps ~~~Emmalyn
