The answer to the given math expression can be determined step-by-step as follows:

Expression:
4 + 2 × 9 – 1 + 7

Step 1: Multiplication First
According to the order of operations (PEMDAS/BODMAS), we must perform any multiplication or division before addition or subtraction. Here, we have:

2 × 9 = 18

So, the new expression becomes:
4 + 18 – 1 + 7

Step 2: Addition and Subtraction from Left to Right
We proceed by performing addition and subtraction in the order they appear from left to right:

• 4 + 18 = 22
• 22 – 1 = 21
• 21 + 7 = 28

Final Answer
The result of the expression is 28.