Two ways of doing it;
(pi*7)^2 = 483.6106156533785723
pi*(7^2) = 153.9380400258998687
Please specify parentheses.
I agree, here, that the language is ambiguous, but you can specify, in words, which interpretation you want.
|\(\pi*7^2\)||What is the product of pi and seven squared?|
|\((\pi*7)^2\)||What is the quantity of pi multiplied by seven all raised to the second power?|
Generally, if you want to indicate parentheses, you will use the term "quantity of..."