To substitute means to replace a variable or expression with either a number, a different variable, or another expression.

To verify whether or not x = 3 is a solution to the conditional equation 2x - 3 = 6 - x, substitute "3" for "x" in the equation and see if the resulting statement is true of false.

Since the result of the substitution is a statement which is TRUE, it has been verified that x = 3 IS a solution to the conditional equation 2x - 3 = 6 - x.

To express a temperature of 20 °C in degrees Fahrenheit, substitute "20" into "°C" given the formula below.

20 °C and 68 °F are equivalent.

To change from inches to centimetres, we could use the following:

z: a length in inches

x: a length in centimetres

x = 2.54z

To change from centimetres to millimetres, we could use the following:

y: a length in millimetres

x: a length in centimetres

y = 10x

To change from inches to millimetres, we could substitute "2.54z" ("x" from the first formula) into "x" of the second formula to create a new formula.

y = 10x    (but x = 2.54z)

y = 10(2.54z)

y = 25.4z

RESULT

To change from inches to millimetres, we could use the following:

z: a length in inches

y: a length in millimetres

y = 25.4z