node_modules/rxjs/internal/types.d.ts(90,44): error TS1005: ';' expected. code example

Example: ERROR in node_modules/rxjs/internal/types.d.ts(81,44): error TS1005: ';' expected.

This problem might arise due to version mismatch. To solve your problem you need to do following changes in your package.json file.
Go to package.json and modify "rxjs": "^6.0.0" to "rxjs": "6.0.0"
then npm update
then ng serve