Given the equation:
\[
2^{x+2} + 2^{x+1} = 48
\]
Step 1: Factor out the common term \( 2^{x+1} \) from both terms on the left-hand side:
\[
2^{x+1}(2 + 1) = 48
\]
\[
2^{x+1} \times 3 = 48
\]
Step 2: Divide both sides of the equation by 3:
\[
2^{x+1} = \frac{48}{3}
\]
\[
2^{x+1} = 16
\]
Step 3: Since \( 16 = 2^4 \), we can equate the exponents:
\[
x+1 = 4
\]
Step 4: Solve for \( x \):
\[
x = 4 - 1
\]
\[
x = 3
\]