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x≈7.5

Step-by-step explanation:

Part A:

Let's call the missing side of x:

5²+x²=9²

25+x²=81

x²=56

x= square root of 56

x≈7.5

Part B:

The sum of the internal angles of a triangle is always 180°, and the square in the top angle means that it is 90°, so:

90°+21°+y=180°

y=180°-90°-21°

y=69°

answer: 414,377,008

step-by-step explanation:

just multiply it