exam Maths Puzzle Numerical Ability

I have about five problems that I could not workout on my quiz and this is one of them 0.4x+2.5=-7.5 can someone work it out in detail for me please.

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exam Other Question

solve by facotring (multiple choice question)

9x^3-40x^2-25x=0

choices:
a: 5/9, -5
b. -5/9, 5
c. -5, 0, 5/9
d. -5/9, 0, 5. Please Help Me Figure This Out!!!!!!!!

Question- A baseball park has 40,000 seats of which 13,040 are box seats and 18,200 are reserved seats. What percent of the seats are box seats? What percent of the seats are reserved seats?