First, since we must follow PEMDAS, we need to do the operation that is first, which is addition.
-3.9 + 6.01 ← Adding a negative means subtracting, then giving the sign of the bigger number.
So now we solved those and we got this answer: 2.11
Now, we need to subtract and re-write the expression.
2.11 - (-7.423) = 2.11 + 7.423= 9.533
Ok....so now we have our final answer, and we have the choices above.
The only answer that matches ours is the last one.
Final answer: 9.533
Hope I helped ^_^
Rational number, because the Square root of 400 is 20, since 20 x itself is 400. Hope this helps!
The simplest answer form would be -5 square root of 7 end root + 7 square roots of 6