Answer
$x=20$
Work Step by Step
"Twice" means multiplied by 2. The term preceding "subtracted from" is the subtrahend. The comma tells us the "twice" applies to "a number" rather than to the difference.
$60-2x=20$ $\longrightarrow$addition property
$60-2x-60=20-60$ $\longrightarrow$combine like terms
$-2x=-40$ $\longrightarrow$multiplication property
$-2x\div-2=-40\div-2$ $\longrightarrow$divide
$x=20$