Help plz its about completing the square

While scuba diving, rajeev dove to a depth of 12.6 feet below the surface of the water and then descended another 8.7 feet. what expression can be used to find rajeev's new position? 12.6 – 8.7 –12.6 – 8.7 –12.6 – (–8.7) 12.6 – (–8.7)

Write the fraction or mixed number and the decimal shown by the model

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827