6.15*
the exponent is a positive 3 so would move the decimal point 3 places to the right 6150.
<span>standard notation is 6150 </span>
Because all of those have the same base of 5 you can just solve like a regular algebraic expression.
x + 4 + 8 = 64
x + 12 = 64
Subract 12 from both sides
x = 52
replace x with 5.75 feet
y = 12(5.75)
12 * 5.75 = 69
the desk is 69 inches long