book Maths Puzzle Numerical Ability

please solve the following inequalities as i am having some difficulties:

4x + 12 >= 36 + 4

8z + 4z < 6z - 12

thank you :)

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book Other Question

5x^4-12x^3=0

these exponents are blowing my mind.
Radical expressions
Three students were asked to simplify sqrt10 +sqrt50. Their answers were:
Sqrt10(1+sqrt5),
Sqrt10+5sqrt2, and
Sqrt2(5+sqrt5).
Which if any is correct?
Which is in simplest form?
Thanks so much