Without using a calculator, find the value of the following:
(a) 2x − y when x = 7 and y = 4.
(b) x² − 5x + 12 when x = 6.
(c) 2m³ when m = 10.
(d) 5fg² + 2g when f = 2 and g = 3.
(e) 2v + 4w − (4v − 7w) when v = 20 and w = 10.