Working out the expression 7(3ˣ) is first to calculate the value of 3ˣ then multiply the answer to 7.
For example, let x = 2
Then 7(3ˣ) = 7(3²) = 7 × 9 = 63
With the same value of x = 2, calculating 21ˣ = 21² = 441, which isn't the same answer with the expression 7(3ˣ)
If the sum of the square of a number plus the triple of the same number equals eighteen, the required numbers are 3 and -6
Let the unknown number be x
The square of the number is expressed as x²
Triple of the unknown number will also be expressed as 3x
Taking the sum of both numbers and equating it to 18 will give;

Factorize the resulting equation:

Hence the required numbers are 3 and -6
Learn more here; brainly.com/question/13805464
Well you would divide distance by time and you should make sure that you do the trucks equation seperate from the cars equation other wise you would only get one answer and it looks like you need 2 so figure out the time an distance for each car then divide distance by time and that is your answer.
Because the 5 repeats the fraction would be 3 and 25/99