7. Put everything you've learned about analyzing sources of historical evidence to the test. Examine this excerpt from a letter written during World War I and answer the questions that
follow. I
October 3, 1915
Dardanelles, Turkey!
Dear Mr. Welsh
The country is really quite pretty and just like the hills and valleys of South Wales, but there
are no brooks or rivers. It rains hard for a month each year usually about this time and then there
is no more until the next rainy season. But although it is so gloriously sunny something is wrong

radioactive dating, also known as  radioisotope dating  is a process that in  estimating the approximate  age  of  rocks. these data can be analyzed from  the studies dealing with the  decay of the radioactive elements that are present in these rocks. in nature, there are a few types of materials or atoms which are quite unstable and they spontaneously decay or breakdown to form other kinds of atoms.

a is the final : )

simplify brackets

8 - 2a - 7 = a + 40

simplify 8 - 2a - 7 to -2a + 1

-2a + 1 = a + 40

add 2a to both sides

1 = a + 40 + 2a

simplify a + 40 + 2a to 3a + 40

1 = 3a + 40

subtract 40 from both sides

1 - 40 = 3a

simplify 1 - 40 o -39

-39 = 3a

divide both sides by 3

-39/3 = a

simplify 39/3 to 13

-13 = a

switch sides

a = -13