Simple expressions use the arithmetic operators + and *, with both numbers and variables allowed as operands. the recursive definition of such expressions is as follows:

1) Any number or letter (i. e., a variable) is an expression.

2) if E and F are expressions, then so are E+F, E*F, and (E)

For example, both 2 and x are expressions by the basis. The inductive step tells us x+2, (x+2), and 2*(x+2) are all expressions. Notice how each of these expressions depends on the previous ones being expressions. Prove that every expression has an equal number of left and right parentheses.

Let us imagine that the number of automobile accidents in a certain region are related to the regional number of registered automobiles in tens of thousands (b1), alcoholic beverage sales in $10,000 (b2), and decrease in the price of gasoline in cents (b3). furthermore, imagine that the regression formula has been calculated as: y = a + b1x1 + b2x2 + b3x3 where y = the number of automobile accidents, a = 7.5, b1 = 3.5, b2 = 4.5, and b3 = 2.5 calculate the expected number of automobile accidents for a football weekend if the region has 25,000 registered vehicles, $75,000 worth of beer is sold, and a gas war causes a 10 cent drop in a gallon of gas.