What is the value of x in the equation x  – y = 30, when y = 15? its not 45 tho

What's the difference between: x≥0 and nonnegative integer. ?

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6

In the triangles, bc =de and ac fe.if the mzc is greater than the mze, then ab isdfelth