If 7 - y = 6, then y=

y =1

Step-by-step explanation:

7 - y = 6

Subtract 7 from each side

7 - y-7 = 6 -7

-y = -1

Multiply each side by -1

-y*-1 = -1 *-1

y = 1

large crystals result from very slow cooling.

evaporation of water: this would produce an evaporite which is a sedimentary rock. like a salt pan in a desert. not possible to have volcanic rocks originate this way.

crystalization in molten earth: slow cooling over time. (hundreds to millions of years)

crystalization at earth's surface: this results in fast cooling. (a few hours to a few months or years)

crystalization from cooling off hot water: that would be a hydrothermal deposit. while associated with volcanics they are not volcanic rocks themselves and usually occur fairly rapidly.