28.50x + 110.99(14-x)=811.45
distribute
28.50 x + 1553.86-110.99x =811.45
combine like terms
-82.49x+1553.86=811.45
subtract 1553.86 from each side
-82.49x =-742.41
divide by -82.49
x=9
He bought 9 of the 28.50 features and 5 of the 110.99 features
Olá!
(2x - 6) + (x+ 10) + (2x + 1) = 180
2x - 6 + x + 10 + 2x + 1 = 180
2x + x + 2x = 180 + 6 - 10 - 1
5x = 175
x = 35
This is a problem of
fact families, but <em>what is fact families?</em> Well it is a family of four things. Two of them are additions and two of them are subtractions. So this question asks about fact families by w<span>riting the <em>subtraction fact two ways</em>. So we have:
</span><span>

First way. So let's take the number 10 and explain this problem using triangles. Let's say that we have 10 triangles in the beginning:
</span>Δ Δ Δ Δ Δ
Δ Δ Δ Δ Δ
So I want to take away 3 triangles, then by taking away 3<em> what is left? </em>Well the answer is 7:
Δ Δ Δ Δ Δ
Δ Δ
That is, if we subtract 3 from 10 then the result is:
Second way. In this subtraction we take the same 10 triangles:
Δ Δ Δ Δ Δ
Δ Δ Δ Δ Δ
Now I want to take away 7 triangles, then by taking away 7 what is left is 3:
Δ Δ Δ
That is, if we subtract 7 from 10 then the result is: