3. __CH4 + __O2-> __CO2 + __H2O
4. __K + __H2O-> __KOH + __H2

3: 1 CH4+ 2 O2-> 1 CO2 + 2 H2O

4: 2 K+ 2 H2O -> 2 KOH+ 1 H2

Explanation:

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).