Evaluate the following expression when a = 7 and b =  − 3.

There is no following expression. How can we evealuate it?

To evaluate the expression when a = 7 and b = -3, we need to substitute the values of a and b into the expression and simplify.

The given expression is not provided, so we can't determine the evaluation of the expression without knowing the expression itself.

However, let's assume the expression is: 2a - 3b.

Substituting a = 7 and b = -3, we get:
2(7) - 3(-3)

Now, we can perform the multiplication and addition/subtraction to simplify the expression:
14 + 9 = 23

Therefore, when a = 7 and b = -3, the value of the expression 2a - 3b is 23.