Answer:
21 birds and 7 dogs
Step-by-step explanation:
Represent Birds with B and Dogs with D
[tex]B + D = 28[/tex] ----- Total Animals
A bird has 2 legs and a dog has 4, so:
[tex]2B + 4D = 70[/tex] ---- Legs
Required
Solve for D and B
Make D the subject in the first equation
[tex]D = 28 - B[/tex]
Substitute 28 - B for D in the second
[tex]2B + 4(28 - B) = 70[/tex]
[tex]2B + 112 - 4B = 70[/tex]
Collect Like Terms
[tex]2B - 4B = 70 - 112[/tex]
[tex]-2B = -42[/tex]
Solve for B
[tex]B = -42/-2[/tex]
[tex]B = 21[/tex]
Recall that: [tex]D = 28 - B[/tex]
[tex]D = 28 - 21[/tex]
[tex]D = 7[/tex]
Hence, there are 21 birds and 7 dogs
