Questions

*  The Gulf of Mexico, bordered by the United States, Mexico, and the island nation of Cuba, is the worlds largest gulf.

*  It has a coastline of about 5,000 kilometers (3,100 miles).

*  The Gulf of Mexico is connected to the Atlantic Ocean by the Straits of Florida, between Cuba and the U.S. state of Florida.

*  It is largely surrounded by the North American continent.

Sum of all numbers in each row and columns must be 15.

In last row to gt sum as 15 missing number must replaced by 1. 

Alum is a common alum, potassium aluminum sulphate K2SO4.Al2SO43.24H2O which makes colloidally suspended impurities in water such as clay to settle down.

Sea appears blue in colour due to the scattering of the rays when they hit water molecules