$\sqrt{? \times 7} \times 18 = 84$

Along a yard $225 \ m$ long,$26$ trees are planted at equal distances,with one tree at each end of the yard. What is the distance between two consecutive trees in meters?

If $x^{2} + \frac{1}{x^{2}} = 1$,then what is the value of $x^{48} + x^{42} + x^{38} + x^{30} + x^{24} + x^{18} + x^{12} + x^{6} + 1$?

If $M = 0.1 + (0.1)^{2} + (0.001)^{2}$ and $N = 0.3 + (0.03)^{2} + (0.003)^{2}$,then what is the value of $M + N$?

Solve for $x: 3^{x}-3^{x-1}=486$

If $x^{3}+3x^{2}+3x=7,$ then $x$ is equal to