Four pine seedling and 3 fir seedlings cost 29.00. Two pine seedlings and 7 fir seedlings cost $42.00 Determine the cost of each type of seedling.

Question

Four pine seedling and 3 fir seedlings cost 29.00. Two pine seedlings and  7 fir seedlings cost $42.00 Determine the cost of each type of seedling.

hero · Answer

4p + 3f = 29
2p + 7f = 42

Multiply the second equation by -2 to get:

 4p +  3f =  29
-4p -14f = -84

Now, you are authorized to add.  (You can only add when eliminating a variable):

-11f = 55

11f = -55
    f = -55/11
    f = -5

Now find p

anonymous · Answer

But why do we mulitipy it by negative 2?

anonymous · Answer

@Hero

anonymous · Answer

?

hero · Answer

Because you need to do that in order to eliminate a variable