In a certain code, if '+' means 'multiplied by', '-' means 'divided by', 'x' means 'minus', and '/' means 'plus', what is the value of the following mathematical expression: 48 - 6 + 6 / 5 x 7 ?

In a certain code, if '+' means 'multiplied by', '-' means 'divided by', 'x' means 'minus', and '/' means 'plus', what is the value of the following mathematical expression: 20 - 2 + 4 / 12 x 7 ?

In a certain code, if '+' means 'multiplied by', '-' means 'divided by', 'x' means 'minus', and '/' means 'plus', what is the value of the following mathematical expression: 24 - 3 + 5 / 11 x 10 ?

In a mathematical substitution cipher, if A = 3, B = 9, and C = 12, what is the numerical value of the expression 'A × B + C'?

In a class of 78 students, 19 study Physics, 64 study Chemistry, and 5 study neither. How many students study both Physics and Chemistry?

If Person A can complete a task alone in 20 days, and Person B can complete the same task alone in 30 days, how many days will it take them to complete the task if they work together?

If Person A can complete a task alone in 5 days, and Person B can complete the same task alone in 20 days, how many days will it take them to complete the task if they work together?