The title psalms was added to the second book of old testament poetry in the ancient greek translation of the hebrew scriptures called the: koheleth septuagint tehillim talmud

A psalm is a sacred song or hymn, found in the Bible and sang during Christian and Jewish worship. Some psalms were added to the second book of Old Testament poetry in the ancient Greek translation of the Hebrew Scriptures called Tehilim. In Hebrew, the title is “Songs of Praise” or Praises” found in  (Tehilim, Psalm 145). These psalms are mostly laments or complaints.  

substitute y = 2x - 4 to x + 2y = 12:

x + 2(2x - 4) = 12     use distributive property

x + (2)(2x) + () = 12

x + 4x - 8 = 12     add 8 to both sides

5x = 20     divide both sides by 5

x = 4

put the value of x to the first equation:

y = 2(4) - 4

y = 8 - 4

y = 4