Let's solve the equation:

$3(7x + 7) = 7(4x + 10)$

Step 1: Distribute the constants on both sides.

On the left side: $3 \times (7x + 7) = 21x + 21$

On the right side: $7 \times (4x + 10) = 28x + 70$

Now the equation is: $21x + 21 = 28x + 70$

Step 2: Move all terms with $x$ to one side and constant terms to the other side.

Subtract $21x$ from both sides: $21 = 7x + 70$

Now subtract 70 from both sides: $-49 = 7x$

Step 3: Solve for (x\