exam Maths Puzzle Numerical Ability

Can you please help me understand the rules and format for this type of math?

(6x^2-4x+7)+(2x^2-3x-9)=

I tried this one,but i cant figured it out?

6x-(4x-5)=13
6x+(4x+5)=13

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exam Other Question

Could you please assist and solve this equation using the substitution method and also tell if it is independent, inconsistent, or dependent? Thank you.

3y = x + 5
3x - 9y = 1 Problem: Joe has a collection of nickels and dimes that is worth $5.65. If the number of dimes were doubled and the number of nickels were increased by 8, the value of the coins would be $10.45. How many dimes does he have?