Answer: Choice C. 
and Choice E. 
Step-by-step explanation:
Algebraic exponents.
If triangles AMN and ABC are similar, then
AM/AB = AN/AC
or
AM/(AM + MB) = AN/(AN + NC)
Check if this is true:
AM/AB = 21/(21 + 9) = 21/30 = 7/10
AN/AC = 14/(14 + 6) = 14/20 = 7/10
The angle at vertex A is common to both of the triangles.
Then by the side-angle-side (SAS) similarity theorem, the triangles are indeed similar.
We know a or b != 0
but a-b==0 so both are the same unknown number
b/a must = 1
so
a/b is equivalent to b/a as a/b=1 as well.
So the last answer choice.
Study. also, i would leave the answer there, but it says i need 20 words to answer so thats why i included this extra bit, but yeah just study.
Answer:
x=8
Explanation:
The picture tells us that the triangle is equilateral (this means that each angle is 60°). We can assume this because each side has been marked with the same line.
Because each angle is equal to 60°, this means that:
7x+4=60
Now solve for x:
7x=56
x=8
