Answer:
35 - 20n
Step-by-step explanation:
Use destributive property.
5 * 7 = 35
5 * 4n = 20n
35 - 20n
Use double angle identity

We can relate '6x' to '3x' in the same way since 6 is 2*3.

Now sub into left side of identity. Simplify until it equals right side.