Fun fact During your lifetime, you will produce enough saliva to fill two swimming pools ‍♀️

fun fact More human twins are being born now than ever before. ...
fun fact A narwhal's tusk reveals its past living conditions. ...
fun fact The first person convicted of speeding was going eight mph. ...
fun fact "New car smell" is the scent of dozens of chemicals.

Wow thank you, I knew the first two facts but I didn't know the other three facts.

Explanation:

thank you, i gained knowledge

That is so awesome had no idea that was a true thing.

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