How can I multiply a variable in VSCode snippets?

    "Print to console": {
        "scope": "jade, pug",
        "prefix": "fimg",
        "body": [
            "img(src='https://fakeimg.pl/${1:350}x${2:200}/00CED1/FFF/?text=$1x$2' srcset='https://fakeimg.pl/$1x$2/00CED1/FFF/?text=$1x$2 1.5x, https://fakeimg.pl/$1x$2/00CED1/FFF/?text=$1x$2 2x' alt='')"
        ],
        "description": "Fake images"
    }

for dimensions 1.5x knife increase the variable $1 by one and a half times, and for the multiplier 2x increase it by 2 times