If there is an int/integer in a array, and the same int/integer comes at the same spot, does it cancel each other out or does it reassing the value? (Java)

Give the equations of two different lines that are perpendicular to the line 3x + 4y = 7.

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning

If 1.4% of the mass of a human body is calcium, how many kilograms of calcium are there in a 165-pound man? 1.0 kg ca 5.1 kg ca 1.0 x 102 kg ca 5.1 x 102 kg ca