Explicitly initialize member which does not have a default constructor

You need to initialize the myObject member in the constructor initialization list:

MyClass::MyClass() : myObject(60) {
   myObject.doSomething();
}

Before you enter the body of the constructor all member variables must be initialized. If you don't specify the member in the constructor initialization list the members will be default constructed. As MyOtherClass does not have a default constructor the compiler gives up.

Note that this line:

MyOtherClass myObject (60);

in your constructor is actually creating a local variable that is shadowing your myObject member variable. That is probably not what you intended. Some compilers allow you turn on warnings for that.

You are almost there. When you create an object in C++, by default it runs the default constructor on all of its objects. You can tell the language which constructor to use by this:

MyClass::MyClass() : myObject(60){

    myObject.doSomething();

}

That way it doesn't try to find the default constructor and calls which one you want.