Mountain climbers can use a map to tell them the of their climb.

The words are topographic, elevation and steepness.

Explanation:

Mountains climbers always need a topographic map to know the elevation of a certain mountain. Elevation and steepness are two variables that appears in a topographic map, this elements tell the climbers the exact information so they can calculate the risk of his climbs.

- three-quarters or two-thirds..

- "the constitution provides that an amendment may be proposed either by the congress with a two-thirds majority vote in both the house of representatives and the senate or by a constitutional convention called for by two-thirds of the state legislatures."

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