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 When you substitute an expression, you replace each variable with a given value.

Step-by-step explanation: When you substitute, you replace some number with another number that doesn't really change the value of the expression.

1. When you substitute an expression, you replace each variable with a given value

Step-by-step explanation:

Substitution means putting numbers in place of letters to calculate the value of an expression. Or replacing the variables (letters) in an algebraic expression with their numerical values.

x = ± 6i

step-by-step explanation:

x^2 = -36

take the square root of each side

sqrt(x^2) = sqrt(-36)

we know sqrt(ab) = sqrt(a) sqrt(b)

x = ±sqrt(36) sqrt(-1)

we know that sqrt (-1) = i

x = ± 6i

x= cost per bracelet

number of bracelets * x + shipping charge = total cost

so

9x+9=72